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 other----is to date the spirits to delay.
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 Crack in the Throne Room. As always a troop of undead guard the periphery of the phenomena. The Crack 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 Crack 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 Cracks. 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 Crack 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 9th 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 escaped 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, that Momonga dates her. She reasons that there may be an event in which a Spirit will emerge in Nazarick and tries to make a convincing argument that having master and her date as a good exercise. Momonga thinks that her idea holds credibility and accepts it much to her shock. Since Momonga has no experience in dating her reason is suitable. Albedo suggestion that they receive cooperation of Kotori Itsuka who will providing advice through a support system while the date us being conducted. Momonga wishes that the date be executed immediately much to Albedo's pleasure.
Kotori is with Entoma Vasilissa Zeta in the Round Table Room, monitoring Momonga's and Albedo's date using the Mirror of Remote Viewing. Albedo waiting in the hallway is joined by Momonga who apologizes for making her wait as he was trying to brush away the dust off his clothes. Albedo states that its alrigh and she guides Momonga to her chamber and asks Momonga to allow her to help take off his clothes. Kotori immediately halts the advances that Albedo is trying to make, stating it too soon to start a relationship like this. So taking Kotori's advice Albedo takes Momonga to other prime destinations in Nazarick to practice dating. Such as Spa Resort Nazarick, Snowball Earth, and the 7th Floor, which all have the same motive to get Momonga to get his clothes off or find an excuse for Albedo to cuddle with her master. Kotori is at a loss of the absurdity of the scenes and realizes that Albedo is just like Origami's perverted behavior towards Shido. Despite the situation, Momonga tries to tell Albedo that the "date" was alright and to cheer her up he allows her to kiss him. This is seems by Shalltear who is angry that Albedo has stolen Momonga's kiss. They two women soon end up in a heated argument over Momonga's affections. Kotori finds it ironic that the date the were practicing to seal a Spirit has now just unleashed chaos in Nazarick.
Meanwhile, Shido is waiting alone in the forest for Dark Tohka's appearance. Attached to him is a wiretap inserted by Origami who insisted it being on his bare chest. She and the other are waiting at a distance to monitor the situation. There she will relay instructions from [Message]s from Nazarick to ensure that his date with the target goes smoothly. Kotori will also be assisted by the protagonists who Momonga recommended in providing dating support due to the protagonist's experience in negotiations outside of Nazarick. In addition Yuri Alpha and CZ2I28 Delta were assigned to guard the area of the date to prevent third party interference..
Dark Tohka eventually descends from the Neighboring World, after locating Shido. When she appears before him, Shido tells her that he does not wish to fight. Dark Tohka s cautious and wants revenge for her previous humiliation. The protagonist provides their input to what to say to the Spirit, giving advice to Shido on when he first kissed Dark Tohka in his own world. Going with that as an introduction, Shido states that he wants to apologize and offer to take her on a date. Dark Tohka is amused and while she can easily kill him, decides to enjoy this "date"
The first part of their date takes them deeper into the forest. Though Dark Tohka is getting bored, Shido introduces her to a cute animal, Hamsuke. However the Spirit is unimpressed calling the magical beast a steel ball. The next part takes them to a plains area but is again rejected. When the reach the Great Lake area Shido tries to impress her with the crystal clear water and majestic mountains, but Dark Tohka is not moved. Shido tries to makes his female companion to remember the time when they were kids and they walked by the sea. However Dark Tohka only has memories of a time when she was in a dark room with humans. Entoma arrives to the scene bringing freshly baked Kinako Bread, a treat that Tohka enjoyed and will hopefully bring back a sense of nostalgia to Dark Tohka. The girl wary that it may be poisoned, stuffs half of it in Shido's mouth to confirm its safe before trying her half. She doesn't remember eating this bread before much o Shido's shock.
Dark Touka then asks him why Shido is calling her Tohka and demands to know what he knows about her. Shido then tells her the events that happened on April 10th when he first met her. Seeing that he named her Dark Tohka demands an honest answer of why he helped her then. Shido states that the the old Tohka rejected everything due to humans reaction towards Spirits and he and her were similar. He could relate as he abandoned by his mother and felt unloved by the world. But he found what he was seeking with Kotorii and his friends such as Tohka did. Dark Tohka is silent in this part of the exchange. In Nazarick Kotori reports according to her device that Tohka's Inverse Form's mood and favor-ability have risen indicating all is well. However just as they those gathered in te room celebrate on the success, the smartphone releases new data showing information to the contrary. Demiurge also states that Dark Tohka has now pointed her weapon at Shido.
Dark Tohka believes that she cannot entrust herself to the like of someone like Shido and demands a duel to prove his worth. If he won't then she promises to kill him. Shido with no other recourse complies and brings out Sandalphon. The rest of Shido's allies come out from hiding as the duel commences. Dark Tohka manages to overtake Shido in the duel. Disappointed in the duel she prepares to kill him, but is interrupted by shots from Kurumi's firearms. The bullets are deflected from her barriers. The Worst Spirit declares that her killing Shido is a problem for her as she has plans to devour him. Taking a stand she intervenes in the fight alongside her clones. Beng assisted by Kurumi, Shido's weapon is knocked out of his hand by Dark Tohka, and she prepares to attack him with Nahemah. She is stopped when a Death Knight block hers. Surprised by the interference, she is temporarily frozen by Kurumi's Seventh Bullet Zayin. Taking the chance, Origami tosses back Shido's weapon who then uses it to disarm his opponent of her weapon.
Slimeko watching the battle is worried that Dark Tohka will resume attacking once temporal freeze effect is gone. Momonga however thinks otherwise and that the entire battle was simulated by Dark Tohka as a form of intimacy. He reasons that his Death Knight confirmed that it did not sense any murderous intent and that Shido was never really in danger. Dark Tohka admits her defeat and thanks Shido for the first time she has positive feelings. She understands that he is important to her other self and relents to entrust her to him. Dark Tohka though warns him not to make her sad and voluntarily kisses him to seal herself. Dark Tohka collapses leaving a sleepy mumbling Tohka in her place.
In Nazarick, Shido and Momonga have a private talk. Shido wanted to personally thank the Overlord for his assitance enduring the crisis. Momonga is just grateful on the information Shido's provided on spacequakes, which he hopes will clarify the existences of the Cracks. So far Tohka has remained normal, enjoying the baked kinako bread provided. Shido is more concerned about returning home worried about his team's absence and the actions of DEM. Momonga understands that the situation happened was because of Tohka's despair. He makes Shido promise him that he will take care of that girl. In another note while Momonga still cannot provide him a definite way to return back to their world, he welcomes Shido friends to remain in Nazarick as long as they want. As Shido leaves Momonga cannot help but be reminded that Shido is like Touch Me.
Outside in the 10th Floor, Shido meets with Kurumi and asks she if she is able to use her powers to travel back in time to the point when they were first sucked into this world. Kurumi surprised that Shido would suggest such action states that is possible, but it will mean all memories what what happened in this world will cease to be. Shido is fine with the result if it means returning back to their world to save the Spirits from DEM. Kurumi happy that she is now a collaborating with Shido is about to agree when a disembodied voice rings out stating it was seeking them and wishes to bring them back.
Everything is engulfed in a flash of light. Kurumi finds herself back in the streets of Tengu City. Confused on what happened she wonders if a primordial Spirit was involved. Shido and the others find themselves back where they were before the Crack suck them into Nazarick. Though confused and awe they have come home they are distracted by a comm from their associates at Ratatoskr who were worried when they vanished. The group thankful they are home rush to greet their colleagues. Shido staying behind silently promised both Dark Tohka and Momonga that he will keep his word. He later is joined by Tohka, who is eager to share some kinako bread to their friends they got from Nazarick.