Yuta and Rikka may finally be together, but things haven’t settled down just yet! The arrival of Yuta’s childhood friend, the extra-eccentric Satone Shichimiya, is about to take this couple’s relationship from delusional to downright crazy. Not only is Satone a full-time chunibyo sufferer herself, but now she’s claiming to be Yuta’s one and only soul mate. If Yuta and Rikka want to make their relationship a reality, they’ll have to break through Satone’s fantasies first!
As the new school year begins, Rikka ends up having to move out of her apartment, since Tōka no longer lives there, and is temporarily living alone with Yūta whilst they search for a new place. Meanwhile, Shinka, who has dyed her hair black in pursuit of a non-chūnibyō second year, continues to be at odds with Sanae. Tōka soon catches on about Rikka lacking a new apartment and confronts her and the others, promptly defeating them. Whilst Tōka initially objects to Rikka living along with Yūta, the issue is soon resolved when Kuzuha returns home for the new school term to supervise them.
Interested in their relationship now they are living together, Shinka, Sanae, and Kumin keep an eye on Yūta and Rikka, the latter of which has ended up spending nearly all of her monthly allowance. After Yūta reveals they had yet to even get to even hold hands, Shinka takes him to meet her friend Kazari Kannagi, who arranges for Yūta and Rikka to go on a date. Yūta decides to take her to the aquarium to see the dolphins, where they start holding hands. As Rikka states her uncertainty over what lovers should do, Yūta decides that he is fine with their relationship staying the way it is for now. Later that night, Rikka meets a peculiar girl that had moved into her old apartment, in much the same way Yūta first met her.
After Yuta is left reeling from a lewd dream about Rikka, he ends up losing a bet against her and is forced to dress up as a magical girl. Later that day, Rikka encounters the girl from before, who is revealed to be Yuta's old friend during middle school and the one who led him to enter his chunibyo phase, Satone Shichimiya. As Satone is invited over to dinner that night, Rikka becomes over her getting awfully clingy to Yuta, particularly when she does her old habit of rubbing her nose against Yuta's. After seeing Satone off, Yuta reassures Rikka by initiating a 'contract' of his own.
Shinka decides to run for student council president, but her candidacy campaign proves difficult due to Sanae constantly interfering. Later, it is also revealed that Satone had gone to the same middle school as Shinka and was well versed in her identity as Mori Summer. Sanae, now convinced that Shinka is the genuine article, starts acting more polite and affectionate towards Shinka, who has her help out with her election campaign. However, this soon turns out to backfire against Shinka when Sanae uses notes from her chunibyo days as an endorsement speech. As such, Shinka fails to get elected and Sanae goes back to believing she is a fake, bringing their relationship back to the status quo.
When a Hobby Group Representative Meeting is held to determine which hobby groups should be allowed to keep their rooms, Rikka's failed presentation of what the 'Far Eastern Magic Napping Society in Summer' does exactly leads their supervisor, Nanase Tsukumo, to investigate what they actually use their room for. Nanase points out the 'napping' part of their group is actually a notable pastime, suggesting they have a 'siesta match' against Maple Hill High School's Siesta Club to serve as an official activity for their group. On the way home, they are approached by Maple Hill's Sui Nemuri, who sparks a rivalry with Kumin, with Rikka rushingly adding she will disband her society if they lose. Thus, Kumin begins training the others in the art of napping, teaching them to sleep in any situation.
Yuta, Rikka, Shinka, and the other second years, go on a class trip to Tsukushino Island, where Yuta and Rikka are notably shy about their relationship. Feeling Rikka can't handle the romance aspect well, Yuta asks Shinka to keep watch over Rikka. Later that night, Rikka comes down to Yuta's room and ends up having to hide in bed with him, where they almost kiss, until Shinka gives them the opportunity to get her out safely. Before returning to her room, Rikka gives Yuta a kiss on the cheek, and the next day they go sightseeing together.
Yuta and Rikka's sightseeing date is interrupted when they come across Satone, who had gotten separated from her own class trip after losing her purse. They manage to help her find it, but Yuta and Satone end up getting chased by a wild monkey in the process. When Rikka spots Yuta receiving an arcade token from Satone, she runs off feeling Yuta had betrayed her, eventually coming across Shinka. As Yuta goes to search for her, Satone calls Kuzuha up, before calling Rikka to meet up with her so they can talk. Satone explains that she once fell in love with Yuta, but threw her feelings away to hold onto her chunibyo identity, leaving Rikka with the question of whether she intends to keep her identity forever and revive Yuta's. After Satone takes her leave, Yuta reunites with Rikka and gives her a new umbrella and charm for her birthday.
Having discovered a website about Mori Summer that neither she nor Shinka made, Sanae meets with who she believes is the true Mori Summer. After Yuta and the others confront her, observing some odd tendencies in the process, Shinka, having nothing to prove herself the real deal, seems to give up and relinquish the name of Mori Summer to her fake. As Sanae feels some loneliness from Shinka distancing herself from her, Yuta and Kumin, who have noticed some curious infactuation Mori has for Sanae, suggests Shinka challenge her for the name of Mori Summer, calling upon Satone to help train her. The next day, as Mori tries to force herself upon Sanae, Shinka brings out her Mori Summer persona to confront her imposter, but is overwhelmed by her delusional power.
Yuta finds an old envelope containing an arcade token similar to the one Satone gave her during the class trip. The next day, Kumin invites Yuta and the others to the beach to help out at her aunt's beach house. There, they are visited by Tōka, who brings her head chef's daughter, Cento, with her. Later that night, as Tōka has a chat with Yuta, Satone notices that Rikka is slowly losing her delusional powers, telling her to decide if she is willing to give up her feelings for Yuta to restore her other persona. The next day, as Rikka and Satone do battle against each other, Rikka recalls her 'special contract' with Yuta and decides to believe in the her that he believes in, giving birth to new delusional powers. Afterwards, Rikka states her determination to be Yuta's girlfriend and still retain her 'Wicked Eye'.
Satone finds herself unable to stop thinking about Yuta, particularly when she encounters him and Rikka at the pool. As Tōka heads back to Italy, she asks Shinka, Sanae, and Kumin to confront Satone and confirm that she is in love with Yuta. Later that night as a Bon festival is held, Rikka wonders off somewhere whilst Satone asks Yuta about his relationship with Rikka, forcing herself to fight through her own heartbreak. Despite her best efforts, Satone is unable to hold back her tears in front of Yuta.
After Yuta finally becomes aware of Sophia's love for him, he seeks advice from Shinka and Kumin. Satone has assured Yuta that she has recovered from her heartbreak but Shinka informs Yuta that Satone's lying and reprimands him for being so dense. Kumin then tells Yuta that Shinka only became upset because she loves him and all her friends and only wants the best for them. Meanwhile, Rikka who has caught a cold from the Bon festival's rain, is still keeping the purpose behind her nightly outings a secret, to Yuta's worry and dismay. Shinka, as Mori Summer, encourages Satone to seek out and defeat her true enemy, who Satone concludes to be Yuta. As she challenges him, Kuzuha informs Yuta that Rikka has gone missing.
As the new term begins, Rikka seems to be ignoring Yuta, with Satone informing Shinka and Sanae that Rikka is thinking about bringing her relationship into the kissing phase. The girls get together at the bath, where Rikka asks them to keep her running away from embarrassment whilst trying to meet with Yuta. With encouragement from Satone and the others, Rikka tries to get her feelings across to Yuta, but still feels too scared to go through with it. Yuta assures her that they don't need to rush things, as he will always love her, though their first kiss is interrupted by news that Chimera had kittens.