Date A Nazarick

Date A Nazarick (デート・ア・ナザリック) is a collaboration game event in Mass for the Dead with characters from Overlord and Date A Live. It was released on March 19, 2020 to April 13, 2020.

Background
Spirit. A special disaster-designated life form that appeared through the Throne of Kings. There are two options. First, destroy the spirits with force. However, because of their high fighting and unknown power, there is a great risk. And the otheris to date the spirits to delay.

Incident
One day after school, Shido Istuka heads to a multi-tenant building in Tengu City, leading to a secret entrance to an underground facility of Ratatoskr. He is later joined by his classmates, Kotori Itsuka, Tohka Yatogami, and Origami Tobiichi. They are talking about the upcoming physical examinations, chatting about how they can avoid it, while being secretly watched by Kurumi Tokisaki. A spacequake soon occurs, signaling the group that trouble will occur. Just as they are about to make preparations for battle, a crack in reality appears behind Kotori, sucking her into the void, followed by the rest of her friends. Kurumi watching from afar it also dragged into its grip leaving behind an empty street.

In the Great Tomb of Nazarick, Momonga and Demiurge are regularly conducting summoning experiments with the Rift in the Throne Room. As always a troop of undead guard the periphery of the phenomena. The Rift flares for a bit, spitting out Shido and his companions. While the students get their bearings, Shido fails to notice the Death Knight looming behind him as he gets up. Origami believing Shido is in danger immediately goes into her Spirit Form and attacks the undead. Kitori tries to restrain her friend in order to get a lay of the situation. However, the Skeleton Warriors surrounding the Rift march in an aggressive manner, giving Origami the justification to attack. She is soon followed by Tohka who also transforms into her Spirit Form believing this to be the work of DEM despite Kotori's protest stating using corpses was a line Westcott would never cross.

Demiurge, watching the scene alongside his master is amused at this as it is the first time their summons have instantly become hostile. Momonga wants things to quiet down, so Demiurge used his skill of Command Mantra to order the newly summoned students to kneel. Shido and the others fall under its influence. Tohka is the only one who struggles to remain standing so Demiurge commands her again to kneel forcing the girl to comply. Momonga slightly intrigued that the girl was able to resist the Floor Guardian's skill, turns his attention to Shido. The young man is paralyzed on the floor and in a position where he is suffocating. Momonga orders Demiurge to help him. Just as Demiurge approaches Shido, Tohka thinking he is going to harm her friend tries to stop him but is unable to move. Looking back at her helpless, she revives the scene where Shido was injured by Westcott. Drawing from the trauma Tohka ignites her Sephira Crystal and goes into her Inverse Form. Her new form allows her to break free of the Command Mantra. Momonga seeing that the situation is growing increasingly more adversarial tells Demiurge to release the girl's friends from his power. Momonga tries to explain that there had been a misunderstanding and introduces himself as Momonga the ruler of the Great Tomb of Nazarick.

Tohka however is acting strangely unable to recognize her surroundings. Now in her Inverse Form, she spots Shido and swears revenge on him. She attacks him with [Nahemah], but Momonga saves Shido with [Wall of Skeleton]. Tenka curses at the undead interference, making the Overlord confused as this girl was this boy's ally and now has murderous intention to kill the latter. Shido attempts to thank his savior for the timely save, but Momonga suggests they concentrate on the current problem. Demiurge also engages Tenka, using [Aspect of the Devil - Eight-limb of Speed] and [Aspect of the Devil - Razor Sharp Claw] to strike her though she is unfazed. Momonga seeing her immune to Demiurge's strongest attacks, thinks that capture may not be possible. Shido tries to reason with Tohka that Momonga's group are not the enemy. She ignores him, seeing that everyone in the room is an enemy. Shido sees that Tohka is now a different person with her own "intention" and "reason". Albedo and Shalltear Bloodfallen, both fully armored arrive to assist them. Tohka seeing this as bugs raises her blade and uses Final Sword: Paverschlev. Shido warns everyone that the slash of the blade could erase everything it touches. However just as Tohka is about to swing her weapon, she stops muttering to herself before vanishing.

Momonga thinking that she is using invisibility is unable to sense her through [Sense Enemy], and neither do the Floor Guardians believe that she is invisible and that she is actually gone. The idea is seen as impossible since [Teleportation] in the New World is near impossible due to the Rifts. Kotori explains that Tohka probably used the Neighboring World to escape due to being in Spirit Form. Momonga still confused on some concepts asks Kotori to explain in greater detail.

From Kotori, Momonga learns about Spirits being human-shaped disasters that originate from the Neighboring World and that she, Origami and Tohka are able to transform into them. In Tohka's case the girl has unleashed the original source of her Spirit's true form. Usually it is sealed away however they can be awaken when a Spirit goes into Inverse as a result of them feeling intense negative emotions such as despair, usually as someone close to them is about to die or immediately after they have died. She reasons Tohka was pushed to this state when she thought Shido was in danger. Albedo and Shalltear protest at the accusation that their comrade Demiurge was going to harm anyone. Momonga is more understanding since it could have been misunderstood the intention based on Demiurge's devil-like appearance. Momonga suggests that they should concentrate on locating Tohka when she emerges from the Neighboring World. He worries that the phenomena of the spacequake may damage Nazarick, Kotori agrees but believes that if she can regain her spiritual power, and trigger a spacequake at the same time with the same magnitude, she’ll be able to cancel it. In addition, Kotori decides to refer this new Tohka as Dark Tohka in order to distinguish the two personalities. However, she states that she is unable to fight her friend as her powers makes her prone to losing control to destructive impulses over the urge of defeating another Spirit. Shalltear sympathizes as it sounds similar to her Blood Frenzy. Shido still opts for a solution that avoids fighting with Dark Tohka. Kotori suggests that can may still be able to seal Dark Tohka and save their friend, by making a date and letting it happen much to Momonga confusion.

Elsewhere in the forest near Nazarick, the Rift located there spits out Kurumi. Kurumi finding no sign of Shido and his friends, wonders where she is. She is suddenly attacked by Chaos Beasts which causes the girl to bring out her musket and pistol and battle.

Back in Nazarick, Momonga learns that the seal on Tohka requires conducting a date with the target Spirit, which will increase their bond and that a "kiss" will be needed to seal the spiritual power of the Spirit. He finds this all unbelievable that a boy like Shido possesses such an ability to seal spirits, though Albedo finds an intrigue to it. Momonga asks the group what are their chances of succeeding with this given the target's hostility. Kotori is pinning on that the original Tohka's feelings or Shido may still exist. All Shido needs to do increase Dark Tohka's liking of him and seal her with a kiss on a date. Momonga seeing his confidence decides to go through with the plan, despite the absurdity. Kotori requires equipment to monitor the date, to provide support and assistance to Shido, which Momonga permits her to use his resources such as [Message] magic and the Mirror of Remote Viewing. Since they lack the proper equipment from the Fraxinus to detect spacequakes, Kotori brings out a prototype smartphone that can detect fluctuations of space and predict spacequake occurrences. However it still requires an artificial intelligence to operate and gives choices to best help Shido win a successful. Momonga though can provide a certain individual with comparable knowledge and expertise in romance and negotiations. Now with their preparations complete the two groups initiate their operation.

Outside of Nazarick, Shido and Origami prepare to search for Dark Tohka and locate an appropriate date spot. Kotori remains behind in the tomb to lend her help in calming potential spacequakes. Shido is worried about the success of their mission especially with Tohka. His silence gain attention from Solution Epsilon, one of the Pleiades who is assigned to guard the visitors from another world. He tells her its nothing, and finds her to be frightening due to the chill she gives him when she looks at him. Origami tries to apologize to Shido for this mess, as if she had not attacked first, then Tohka would not have gone into Inverse Form. They are interrupted by the appearance of a feral bear and two wolves which the Pleiades identify as Contaminated Beasts. Solution along with her sisters Lupusregina Beta and Narberal Gamma make short work of the beast with the help of Origami. After the battle Shido resumes the conversation he had with Origami and tells her that it was not her fault as his cries for help were what set her off. The best they can do right now is focus on the mission to help restore Tohka. Tohka is touched by Shido's words, but they are again interrupted by the maids who wish to focus on finding a suitable location for the impending date.

Kurumi still wandering the Tob Forest encounters a what appears to be two dead trees. The trees attack slashing at Kurumi with its roots, causing the girl to collapse on the ground. The treants are about to calim their prize, when they are shot with bullet, revealing Kurumi still alive. The one on the ground was a clone she created and is joined by a horde of clones that eagerly prepare to attack the monsters.

Shido and the others are looking in the Tob Forest for a spot that is isolated so that the date can be conduct without interference. Deep in the forest they find a dark area which Origami believe swill help the mood for the date with Dark Tohka. A gunshot is heard causing Lupusregina and Solution to investiagte. The latter changes into her Soi persona and order Narberal to guard their charges. The maids head to where Demiurge Enhanced Treant farm is situated and find a bewildering scene. Several young women with the same exact appearance battling with the treants. Solution seeing there is something abnormal going on tells Lupusregina to be on guard. Lupusregina orders the other girl to stop what she is doing. Kurumi taking note of the two, sees that the do not find it strange that these plants are moving and attacking her. She asks if these treants belong, but is met with silence. At first she sarcastically states that she was attacked by the treants and now just wants to run away. Seeing that they understand her Kurumi decides to interrogate them to learn more about where she is signalling her clones to approach the maids in a hostile manner.

Solution and Lupusregina manage to eliminate all the clones and are now engaged in a battle. Solution dodges the shots made by Kurumi, though the other woman gets behind her forcing the Pleiades member to use her slime abilities to evade her. Solution estimates Kurumi to be around the strength of a Guardian and Kurumi likewise sees that her opponents are not humans. Just as the fight gets serious, Shido rushes out and tells everyone to stop. Kurumi and Shido immediately recognize each other, prompting the fighting to cease. Now that everyone is gathered in the area, Narberal asks if Kurumi is Shido's ally. Kurumi admits that she aims to consume Shido, however given that his life may be threatened by Dark Tohka, she offers to cooperate with them to protect and also to avoid fighting the maids. Shido knowing her better accepts her help. The other women are unsure but Origami manages to convince them to support Shido's decision. Solution then takes the opportunity to give her report to Momonga back at Nazarick.

At the Nazarick, Kotori and Albedo are talking in the hallways of the 10th Floor. Albedo admires Kotori not only for providing her knowledge on the spacequakes, but also for her self sacrifice. She sees through Kotori's other reason to remain behind at Nazarick, while her comrades look for Tohka. When Dark Tohka escapede Nazarick, there was no one to take the blame for the travesty in order to convince Momonga that she and her friends were not enemies, she voluntarily stayed behind to act as a hostage to ensure they hold unto their part of the arrangement in securing Tohka. Despite her dangerous situation, Kotori states that it was necessary and her duty as a commander. And Albedo is interested in gaining a little cooperation from Kotori, piquing the other girl's interest.

Albedo then meets Momonga at the Round Table Room, where he is making contingencies for a possible fallout if the "date" with Shido and Dark Tohka fails. Albedo comes and offers a suggestion.

Aftermath
To Be Added...