Brave And Undead Are Too Careful (勇者と不死者が慎重すぎる) is a collaboration game event in Mass for the Dead with characters from Overlord and The Hero is Overpowered but Overly Cautious. It was released on September 15, 2020 to October 15, 2020. The event was re-released on August 2, 2021 to August 16, 2021.
During a summoning experiment by a reaction of the Throne of Kings with the Chaos Stones. This time, three goddesses and one hero appeared in front of Momonga. The goddesses should also be careful, but the reaction, behavior, and judgment immediately after the summoning, the brave man was too cautious as Momonga was wary.
In the Divine Realm, Seiya Ryuuguuin has finished his morning run, stopping at the temple roof where Valkyrie is painting. The hero deciding to take a break gives Valkyrie the opportunity to draw a sketch of him. She tells him not to move so she can finish her "masterpiece" not wanting a repeat of what happened when Crossed Thanatos destroyed her last painting.
The two are soon joined by Ristarte who is curious to see what they are doing. Seiya claims that he initially wanted to resume training but now is forced to act as an exhibitionist for a talentless goddess. Ristarte scolds him for using such language and to bear with it as a senior goddess could erase a world. Seiya asks what she is doing at the rooftop, to which the goddess claims to be taking a break after trying to do her 'best' when she felt she tried too hard and damaged her skin. Seiya doubts the effort she putt in. The talk annoys Valkyrie who is still trying to paint her picture, telling the interfering goddess to be quiet. A third joins them soon, Adenela who has been seeking Seiya so he can live up to his promise to spend time with her on his next visit to the Divine Realm when she helped him against Crossed Thanatos. The hero objects as the deal was that she stopped him which she failed in doing so. This infuriates Ristarte as he cannot go back on his word.
Valkyrie having enough of the interruption goes in an outburst, when a Crack manifests before the group. While the three deities are confused by the phenomena, Seiya on instinct impales a sword into the ground. The reason for it soon becomes clear when the crack in space begins sucking the goddesses into it. They are grabbed from the air by Seiya who is using the sword to ground himself. Ristarte surprised by his initiative asks how he could predict such a thing was going to happen, but is given the answer that Seiya did not, and only assumed that the Crack was a threat. Before he could give orders to Valkyrie to use her [Valhalla Gate], a sudden sword slash comes from the Crack and cuts through, damaging Seiya's blade connecting to the ground. Through the Crack, Seiya sees the form of an undead wielding a scythe lurking on the other side. It attacks again with a sword slash and the blade Seiya is holding onto is destroyed, and with it the last support holding the group to the ground. They are sucked through the depths of the Crack in a blink of an eye.
Meanwhile in the Great Tomb of Nazarick, another annual summoning experiment is initiated using Chaos Stones and the remains of the Throng of Kings. The Crack then spits up the three goddesses in a heap. Ristarte who was just about to get back on her feet, finds herself used as a cushion by Seiya. Upon landing on his partner the hero is glad to know that the ground is safe as it has yet to dissolve the goddess to the latter's indignation as being used as a foothold to check the environment. The goddess is allowed to get up and survey her surrounding which to her discomfort appears to be in the midst of a flock of undead. Seiya seeing the situation decides to call for a hasty retreat and orders Ristarte to summon a [Gate] to escape. A [Gate] portal soon appears in the Throne Room, but before the group can go in, Seiya stops them to check if it's safe. Using a pebble he tosses one into the [Gate], only for the portal to spit out the object into Ristarte's face. Seiya wonders out loud why the [Gate] is not working properly and asks his companions if they know or have seen anything like the Crack, but they are unable to give him an answer only for Ristarte to say that they might not be in the Divine Realm anymore. The thing they came through seemed similar to a [Gate], but it should not be possible for three goddesses to descend into the world simultaneously.
In an irregular situation, Seiya spots Demiurge and Momonga calmly observing the party. Momonga decides to introduce himself as the ruler of the Great Tomb of Nazarick and offers to answer any questions they have on this strange occurrence. Valkyrie however is not in the mood for listening as seeing their calm demeanor accuses them of being the cause of the Crack that brought her and her friends to this place. Most of all she holds them responsible for destroying her work of art that she painstaking worked on and was lost in the commotion. Finding it unforgivable she prepares to attack, but is stopped by Seiya stating that they cannot afford to lose her now. Mistaking this to be a form of declaration of love, the other women swoon at the statement, though Seiya in truth did not want to let their party's strongest member go to waste but lets the women think otherwise so to remain discreet on Valkyrie's power. Seiya calmly assesses the situation they are in, commenting that the ones in front of them might not be responsible. And while they look like undead, this world is not Gaeabrande so in logic undead here might be different in their previous world and possibly not hostile. They should then try to avoid starting hostilities as they might be more powerful than them as this world's laws might just make goddesses vulnerable as they could have instant death magic. Valkyrie seeing his point and pacified by his earlier statement concedes. Momonga watching from afar is surprised how intuitive the young man is as he was just preparing his death magic [Grasp Heart] should the situation turned south. But now that the undead has the strangers undivided attention he then believes he should get to the start and ask how they came to their world.
After sharing information on what they deem acceptable, Seiya and Momonga still regard each other with caution. Though the hero understands that his comrades are in another world, and according to the Overlord, the summoning phenomena that brought them through the Crack was not caused by Momonga to intentionally spirit them away. However, it seems that their experiment may have been a trigger of sort for the Crack. Ristarte inquires about the mysterious undead they saw in the Crack which apparently the beings of Nazarick have no idea of. Seiya doubts Momonga's truthfulness and considers the possibility of him lying to them. But also brings the possibility that there is another enemy out there that seeks to do them harm from the Crack. He is even more wary of the Overlord as his [Ability Perception] is unable to read the status of the former making him think that Momonga is a similar existence to Crossed Thanatos. Likewise Momonga is wary of the new arrivals with Seiya claiming to be a hero summoned to save a world and that his three female companions are goddesses. Momonga's use of [Life Essence] and [Mana Essence] confirms the women to be of considerable power, but he can't exactly measure their HP or MP levels.
Both leaders of the two parties have one thing that they agree on their perspective of the other party: "they're careful." Negotiations begin to determine that Seiya and his companions will stay within Nazarick. Momonga informs the visitors that the dungeon which they are in is currently kept as a secret to the world and that he wishes to maintain the secrecy. Seiya has no qualms about that opting for his group to remain in Nazarick until he can confirm the safety outside. For their temporary residence in Nazarick, Momonga requests that they complete some acts of service for him. Seiya agrees to this, unless all contents of the jobs and information are not disclosed to them, which includes break times, hazards, and holidays. The two go through careful negotiations so that there is no room for misunderstandings and no missteps while Seiya's group are under the custody of Nazarick.
After some discourse between the two leaders and some suggestions from Demiurge, Seiya's party is granted quarters in the 9th Floor guest room. Ristarte is finally relieved that the talks are done and that they can rest. Valkyrie though believes that making a deal was bad and they could have done better if they broke out. The younger goddess is prone to agree as though the undead were formidable, they pale in comparison to Valkyrie. She is quickly hushed by Seiya with a whack from her head as he is paranoid that the room may be under surveillance. He is still uncertain about many things like if the goddesses' immortality is maintained but doesn't wish to take risks to confirm it. After few words from Valkyrie about letting the worries wait until tomorrow, the hero decides to go rest, and begins stripping his clothes. Ristarte misunderstands that Seiya wants to get in bed with Valkyrie and clearly opposes such behavior, covering her own obvious feelings for him on the basis that sexual activity between gods and mortals is prohibited. Adenela is drawn to the conversation and unsheathes her blade to prevent any funny business. Only Valkyrie is unperturbed by the situation, scolding her companions for their lack of sense and making things weird. Seeing that rest is out of the picture, the hero then decides to train by doing push-ups as the goddesses glare at each other in suspicion.
The next day the goddesses and hero find themselves in the 6th Floor, which amazes them as they believe that they are outside. Aura Bella Fiora and Mare Bello Fiore appear to act as their guides. Though they appear to be just children, Seiya is cautious warning his friends that since they are Momonga's subordinates they could be beings with powers rivaling a Demon King. Ristarte is shocked that he would go far as to say such things about such cute children, and tries to apologizes to the elves. To her inherent shock the elves comment how keen the young man is, admitting that they are as deadly as he believes. Seeing that he has been valid, Seiya warns his friends that the place around them might be fake with the intent to trap them. Aura interjects stating that while the 6th Floor was an artificial environment it was not constructed to serve as a trap for the likes of them. The time for Chaos Beasts is nearing and is Aura directs them to the forest where the Crack is located. Upon seeing their adversaries, the Chaos Beasts, the goddesses and hero don't know what to make of them. Since he is unable to perceive the stats of the monster with [Ability Perception], he tells Adenela to attack first. To give her encouragement, he tells her that it's because she is "the best" fighter out of all them. Upon hearing the praise, the goddess goes forward and cuts several of the monsters down. Confirming that they can be killed, Seiya then orders Ristarte to prepare for recovery magic and for Valkyrie to wait in reserve, intending to keep her abilities secret. Valkyrie annoyed that she must restrain herself complies to keep their advantage among their new associates. Seiya then unsheathes his dual blade skills: Double Eternal Sword EX and Phoenix Drive.
The hero completely eliminates all the Chaos Beasts in the attack. Aura observing his abilities comments that even she can't see the limit to his power. Once the monsters are all defeated, all that remains are the Chaos Stones that need to be collected by the Death Knight and the undead minions. Aura announces that the Crack has subsided in releasing Chaos Beasts for the time being and thanks the group for their efforts. The shortness of the battle seems to be a relief, however, Seiya believes that it's not over. He argues that even though the Chaos Beasts have been defeated, leaving no corpses save for Chaos Stones, that they could still be alive. In very minute invisible particles, possibly hiding in Nazarick waiting to regenerate at the opportunity. Aura is confused by his logic though it sounds credible as Nazarick still knows very little about the origins of the Chaos Beasts. The twins believe that they should report to Momonga on Seiya's theory, but the cautious hero instead opts for another path and proceeds to bombard the forest area with multiple [Hell's Fire] with the intent to eradicate the invisible particles that may or may not exist. The elves are aghast at the inferno that was their territory, unsure if Seiya's actions warrant such overkill as there are safe methods of contamination. Seeing the paranoid human torch their forest, the elves wonder if his actions constitute as an attack on the dungeon. Ristarte afraid of immediate retaliation begs them for forgiveness pleading that Seiya is mentally ill.
In the Round Table Room, Aura and Mare give their report to Momonga, Albedo and Demiurge on Seiya Ryuuguuin's team's progress and arson attempt on the 6th Floor. Aura honestly didn't think that the human had any ill intention to attack Nazarick, but she wondered if maybe she should have stopped him. The only reason why she and her brother paused in attacking Seiya was due to his theory that Chaos Beasts could be self-regenerating from small particles even though they vanish and leave behind drops. However, after thinking for awhile, the twins deduced that the theory was implausible as Momonga would have already anticipated it and the current security system in Nazarick is more than enough to deal with intruders that randomly appear in the dungeon. Momonga though is surprised why he never came up with with that theory, as he always assumed the Chaos Beasts were similar to game mobs but comes to the same reason as the elves that the danger was negligible. The two apologize for not preventing Seiya from damaging the forest on the 6th Floor, however, Momonga says that it doesn't matter as the fault lies with him for not telling them about the possible dangers about self-regenerating Chaos Beasts. And as for the damage, it's mostly minor. He wants their report on Seiya and his companions. Aura after using her abilities confirms that the so-called goddesses have greater powers than Seiya, proving her master was right to be cautious. As for Seiya, she and Mare personally find him somewhat cowardly as he made one of his companions fight first to confirm that it was safe to fight the Chaos Beasts. She thinks that it has to do with him being the "Hero" that needs stay alive in order to save the world of Gaeabrande. Momonga mentally wonders if the hero's caution is really based on cowardice, wondering if it might stem from something else. His thoughts are disturbed by Aura who asks if he is alright. Momonga states that he was merely thinking about the possible damage Seiya could unintentionally cause and then directs his attention to Albedo who he asks if preparations are made to handle the mysterious third party that their visitors encountered when they where sucked in the Crack. Albedo reports that everything is prepared to be on the lookout for such an individual from the Cracks in Nazarick and for insurance they plan to place surveillance on their guests when they leave for their mission outside of Nazarick. Momonga is pleased to hear this, and tells his followers to be on guard as he suspects Seiya may have intentionally caused the arson to have his team deliberately transferred outside the dungeon. With this in mind, careful monitoring of the group is necessary.
The goddesses and hero are brought to the Great Forest of Tob. Valkyrie complains about being assigned to another forest again, but Adenela finds it comforting that they are allowed some liberties. Seiya breaking the positive mood, warns the women that this could be a test to see if they escape. Solution Epsilon acting as their guide explains the circumstances of her identity while outside Nazarick and introduces her sister Narberal Gamma who is also present with Slimeko and the protagonist. For this mission Narberal informs them that their activities will not just be limited to hunting Chaos Beasts, but also hunting for food. For this, Ristarte apologizes to their guides for the last item. Prior to the group being sent to the forest, the goddesses and hero had the opportunity to visit the maid cantina where they were in awe at the ludicrous food and area that was comparable to the Divine Realm. However, they were forbidden from even eating the food as Seiya believed that the food was poisoned. Ristarte objected to his paranoid claims, citing that the other diners showed no ill signs, only for Seiya to be convinced they were immune or taken a prescribed antidote. Even if they prepared their own food in the kitchen, Seiya believed all the materials could not be trusted and neither could Ristarte, as her rice balls could kill people. He was convinced that the food might be poisonous to gods or even humans given the heteromorphic species that lived in Nazarick. The hero even rejects the use of poison healing herbs from Gaeabrande confident that since they were in another world, they would not work. To sustain themselves he offered the goddesses what bits of dried meat he carried.
Back in the present Ristarte complains that the hero used this as a basis for even preventing the women from showering, maintaining a strict belief that the facilities and luxuries were not suited for their kind. Seiya believes it to be insignificant in their survival much to the goddesses annoyance on his lack of hygiene. Slimeko watching the exchange comments to the protagonist that the human is definitely overcautious. The protagonist sees that there is a mark of experience and that it seemed to be from a psychological trauma. But when the protagonist comments on Seiya's personality as being experience, he is snubbed by a tempered Ristarte. Narberal already disliking the inferiors is then angered at the insult on her colleague. Valkyrie seeing the displeasure on the other woman's face tries to goad Narberal to say it aloud. Solution quickly intervenes and apologizes on behalf of her sister. Seiya also comes warning Valkyrie to remain calm less they give their hosts a reason to attack them. The tension in the group calms down, though Ristarte wonders how long it could last due to Seiya's uncompromising behavior. To get back on track of hunting for food, Slimeko announces that their prey will be wolves.
After hunting for provisions, the party then heads to the local Crack. Seiya puts an end to the emerging Chaos Beasts with his skills. Ristarte glad that they succeeded in their mission and acquired the food they need is eager to head back. Valkyrie is less than pleased as she is impatient to return home. Fed up with waiting, the Goddess of Destruction decides to unrestrict herself and call upon Ishtar for an Order to open up a [Gate] confident that the senior goddess would hear her and lock in their position. Seiya tries to stop her stating they don't know the risks but his words fall to deaf ears. The Crack is noticed by Solution to be glowing despite the Chaos Beasts having been eradicated. Valkyrie's stats explode to the max as she waits for her ticket to the Divine Realm. A looming shadow soon appears behind. Seiya tries to warn her but Valkyrie is attacked from behind. Seiya deduces that its the same entity that caused them to be sucked into the crack. Dubbing it the name Grim Reaper Seiya believes that Valkyrie's Order rather than alerting Ishtar had alerted it to their location. Valkyrie now angry at being struck from behind and finding an outlet for her disgrace is eager to beat the reaper. The agents from Nazarick also join to fight against this new foe.
During the fight Valkyrie tries to activate her [Omega Valkyrie] skill but is attacked by the Grim Reaper when she attempts to do so. It seemingly disappears and reappears attacking its opponents. Seiya notes that the entity seems to be aware that Valkyrie is more dangerous hence why its preventing her from using her full powers. Worse, he cannot even read the status of the monster. Narberal tries to launch a spell at it, but before she finishes it appears behind hand prepares to strike her. She is saved by Valkyrie who blocks the attack. Seiya orders Ristarte to fly to act as bait for the Grim Reaper. Though insulted at such a role, the Goddess of Healing complies and gets the Grim Reaper's attention. She is attacked and forced to hid behind Valkyrie, who is then protected by Adenela who successfully lands [True Continuous Sword Attack]. However, the attack has absolutely no effect. A retreat is then called by Seiya to his allies. Narberal agrees, taking Slimeko and the protagonist to safety with [Fly]. To cover their escape, Seiya casts a [Meteor Strike] to crush the reaper. The remaining party members escape into the forest, leaving behind only a crater. When the smoke dissipates the Grim Reaper is revealed to be unscathed.
The group relocate to a cave which has been sealed with a giant boulder by Seiya. Despite Solution claiming that they are safe, Seiya sweeps the area again to be sure, for which Ristarte berates him for his rudeness. Solution says that it is okay as she would do the same in their shoes, making Ristarte realize that the denizens of Nazarick never fully trusted them. Seiya returns from doing his survey of the cave, though comments that he would be more sure if he did a [Maximum Inferno] to make sure there are no enemies, but considers that it may bring the roof down. Ristarte asks what's their next move. For the Grim Reaper, Seiya thinks it might be something from between worlds. The [Gate] that Valkyrie called for from Ishtar might have reached the Divine Realm and may show up, however the Grim Reaper might be waiting for them. Seiya predicts that there are 976 ways that the Grim Reaper might attack. Going on what they know on the unknown individual, the group agrees that the Grim Reaper seemed to be immune to any attack they could throw at him. He also seems to be keenly aware of Valkyrie being a larger threat as he singled her out and continued to prevent her from unleashing her abilities. In addition, the Grim Reaper has some control over time allowing the individual to seemingly vanish and reappear in an area. Though space transfer magic is impossible due to the Cracks, the Grim Reaper is apparently an exception.
While Seiya's group try to come up with some countermeasures, back in Nazarick, the protagonist reports to his master on his comrades' situation. Momonga already has seen the devastation caused by the [Meteor Strike], using the Mirror of Remote Viewing, has already sent Mare at the scene to try and repair the damage to the terrain. Unfortunately the Grim Reaper has also vanished from the area. So far from what Momonga can determine, the Grim Reaper is targeting Seiya's group and has an interest in Valkyrie. Though Momonga considers having his subordinates withdraw and let the unknown assailant have Seiya and his friends, the undead cannot discount the possibility that the Grim Reaper might attack Nazarick next. In order to defeat the threat, Momonga believes that it's best to work with Seiya, despite the risk that the latter might be in cahoots with the Grim Reaper. He orders the protagonist to connect him to Seiya so that they can negotiate to join forces.
However, getting Seiya to agree to an alliance is more difficult as the young man refuses to compromise despite Momonga having experience in fighting foes with time-space manipulation techniques. Moreover, Seiya refuses to concede for help as he has suspicions that Momonga might be dealing with the Grim Reaper from behind the scenes and even accuses that Nazarick is using this to make Seiya's group in debt to him and give him credibility. He refuses to become Momonga's pawn, even telling him that he suspects the undead's intelligence to be a farce using misunderstandings and accidental coincidents to maintain an air of intelligence that even fools those like Demiurge. Momonga neither confirms nor denies this, briefly experiencing a small emotion then suppressed outburst. Instead Momonga turns the tables on Seiya by doing his own psycho-analysis of the hero of his own. Momonga points out that Seiya is cautious beyond limit, so careful that it could be registered as being psychologically ill. Using opinions from his subordinates Albedo and Demiurge, Momonga paints Seiya as being a man who doesn't seem to be afraid of "death". Rather he acts cowardly to hide his rational decisions to achieve his goals. Momonga notes that when he sent Adenela against the Chaos Beasts it was just a way to measure the threat level. Seiya's acts of preventing his friends from eating the food or bathing facilities in Nazarick. He knows that Seiya is not a coward who's afraid of dying, but in fact he is a coward who's afraid of losing what is important to him.
The statement of his true nature briefly makes Seiya hesitate in his response. Momonga though responds first stating that he doesn't care if Seiya is afraid to take risk and doesn't want to trust him, but at this point it's unreasonable to not accept help. Momonga warns the hero of the consequences if he gets one of his own hurt when he could have avoided it. Should any of his friends' children are harmed, Momonga will become Seiya's enemy. Seiya finally finding some common ground and united by their need to protect their loved ones, finally agrees to accept Nazarick's aid but still maintains his caution, stating he won't accept a plan even with a 1% chance of losing.
After the two finish going over the strategy, Seiya rejoins the others in the cave declaring that he formally accepted to join forces with Momonga and Nazarick. He informs the Nazarick agents that Momonga will be shortly contacting them to tell them the details of their operation. Ristarte stunned at his trust in their hosts and lack of cautiousness asks him if he is alright, to which he confirms that he is perfectly ready.
The joined forces then relocate to a plains area, in addition arrangements were made by Nazarick to provide anti-time-stop countermeasures. Ristarte is still unsure that their plan whatever it is will work. Seiya though tells her to just focus on her task to heal the injured. They are interrupted when the Grim Reaper soars from the sky and crash before them. Valkyrie seeing her opponent eagerly wants a rematch. The fight drags on and displays that while the Grim Reaper can no longer use its time stop technique it is still very quick. Seiya is fine with how things are as this was planned by him and Momonga. Now that the entity is busy with Valkyrie it has left its blind spot exposed. Ristarte though argues that none of their attacks seem to affect it, but Seiya demonstrates that not all attacks are ineffective. Raising his hand to the sky he demonstrate a technique taught to him by Valkyrie, [Valhalla Gate]. Summoning the gate effigy the Grim Reaper is pulled into its maw and impaled numerous times until the spell ends. It and the Grim Reaper vanish, but not without cost as Seiya begins to to bleed out and spew blood. Ristarte horrified at his sacrifice tries to heal him, but even with her unrestricted use of healing magic, it is not certain that it will be enough. She berates him for using a technique like that demanding to know what happened to his no risk philosophy. However, the danger was acceptable to Ristarte shock as Seiya negotiated with Momonga to provide personnel to heal him. Sebas Tian, Pestonya Shortcake Wanko, Lupusregina Beta and Solution all provide their healing skills to restore the hero to full health. While happy her hero is healed, the Goddess of Healing is insulted that Seiya would call in this much help, thinking that he didn't trust her to bring him back.
At the Round Table Room, Seiya and the goddesses provide their report to Momonga who is pleased that they were victorious. Seiya humbly states that it was due to Momonga's help that the victory was possible to which Momonga states that thanks were not necessary as he was able to observe some interesting things that he believes may benefit Nazarick. Likewise, Seiya found his experience at Nazarick enlightening hoping to use it to help save Gaeabrande. Ristarte is stunned at the change in relationship, as just days before they were wary of one another and asks how this came to be. The two are mute on the mutual respect they now share stating that it was only natural for them which only serves to infuriate her. Though annoyed that she is in the dark she is happy to see some of her fellow goddesses finally getting along with the other Nazarick denizens. Eager to relax, Ristarte tries to tell Seiya that she rented the kitchen to make a meal for the group, when she hears the voice of Ishtar. Ishtar reveals that the Divine Realm has been in an uproar since the disappearances of the three goddesses and hero. Ristarte after listening to her senior, informs the rest of the group that they are being called back immediately. Soon enough a circular [Gate] appears in the room. The goddesses and hero turn to their host Momonga for parting so abruptly, though the Overlord takes no insult deeming their recall to be urgent. Just after they say their farewells, Seiya stops the goddesses to check to see if the [Gate] is safe calling for a live specimen to test its functionality. Momonga watching the hero's prudence to danger makes a note to himself to live by the latter's example.
Once the goddesses and hero are back in the Divine Realm, they underwent a thorough interrogation process conducted by Ishtar and Ariadoa. Now that they are released, Ristarte is finally looking forward to getting some food an rest. However Seiya reflecting on his experience in the incident, thinks that his level of prudence is still lacking. To compensate for that, he envisioned 7,963 possible dangers that may be awaiting on Gaeabrande. To prepare for these dangers, he states his intention to train Ristarte, Mash and Elulu to respond to such situations to prepare them. The Goddess of Healing is relieved that Seiya is back to his old self but tries to slow him down by stating that that they need time to eat, shower and rest. Those concerns are ignored by the hero as he takes the training to be the utmost important. Grabbing her by the hand, he drags her along to go and train with him. Ristarte tries to get Valkyrie and Adenela to help her but they either don't want to get involved or side with Seiya. Dragged with the hero, Ristarte laments to herself that the hero is really overpowered by his overly cautious mindset.