The members of Senkō High School's literature club become shocked when Jurai Andou, a boy usually known for his 'chunibyo' delusions, suddenly develops superpowers of his own. Six months later, each of the club members have since developed their own superpowers, which they put to the test in their monthly check-up. When student council member Mirei Kudou comes to check on the club, she ends up misinterpreting Jurai's chunibyo behavior and inadvertently reveals that she herself has developed superpowers as well. Mirei challenges the club to a superpower battle, using her own ability to steal Jurai's "Dark and Dark" ability, only to find it to be nothing more than a useless lukewarm flame. With the other members knowing not to show off their powers before her, Sayumi easily beat Mirei in a physical match. Learning that Mirei learned of the club's powers from an anonymous text, the group become curious about just who sent it.

Mirei receives an elaborately-phrased letter from Jurai, intended to give her ability the name of "Grateful Robber", but misreads it as "Grateful Lover", misinterpreting the letter as a love letter and declaring herself to now be Jurai's girlfriend, leading the entire club, Jurai included, baffled. After having to deal with both Mirei's over-the-top affections and the jealous glares of the other girls, Jurai explains the situation to Mirei, who seems heartbroken from being turned down. As Tomoyo Kanzaki comes to cheer up Jurai during his moment of guilt, he explains he chose that particular name for Mirei's power so it would match the others and show that she was one of their friends. Afterwards, Jurai receives an e-mail from Mirei apologising for the misunderstanding and accepting the name he gave her power.

The literature club have a recreation day spent playing tennis with their abilities. Later, as Jurai goes off to search for his misplaced "Bloody Bible", the other girls reflect on how he, despite his odd behavior, has been helping them all this time. While retrieving his book, Jurai comes across an alumnus named Hajime Kiryuu, who seems to share his passion for chunibyo naming. He is later revealed to be Tomoyo's older half-brother who left home a year ago. The next day, honorary literature club member Chifuyu Himeki appears before Jurai, stating she has quit elementary school.

Jurai carried Chifuyu on his back to her school before he met up with Kuki Madoka and proceed to go to go to his own school. Later, the club use Chifuyu's "World Create" ability to dress up in various cosplay outfits, after which Chifuyu's aunt, teacher Shiharu Satomi, mentions that Chifuyu had left school early. Later, Chifuyu shows up at Jurai's house after getting into a fight with her friend, Madoka Kuki, who told her not to spend time with the Literature Club anymore. Things get worse between them due to Chifuyu being unable to tell Madoka about her powers, leading her to believe she likes them more than her. Jurai attempts his own dubious manner of trying to get the two to make up, but Chifuyu accomplishes this on her own by having Shiharu help her win Madoka a plush to match with hers. Afterwards, Chifuyu reveals that her wanting to quit elementary school was from a desire to skip grades and enter high school alongside the other members.

Jurai buys himself a guitar, which he risks in a game against Chifuyu. Whilst retrieving his bag later that day, Jurai learns that Tomoyo is trying to become a novel author, being surprisingly supportive. Tomoyo feels pleased the next day when she passes the first round of a light novel award, so Jurai invites her to lunch on the weekend to celebrate. As the two spend time together on what many would see as a "date", element manipulator Hatoko Kushikawa is shocked to see them together.

After working with the Literature Club members to make a personalized video game for Jurai's birthday, Sayumi Takanashi, who has the power to revert things to their original state, catches a cold. Jurai pays Sayumi a visit at her house, where he meets her younger sister Maiya, though Sayumi attitude suddenly changes when Jurai bring up how she was the student council in middle school. The next day, after Jurai hears from Maiya about how Sayumi had originally wanted to join the student council during high school, Mirei theorizes she may have turned it down due to her powers. This leads Jurai to recall an incident that happened ten months ago in which Sayumi, who suggested they use her "Root of Origin" ability to remove everyone's powers, battled against Jurai who was against it. The result of that battle showed that Sayumi's power could not erase Jurai's Dark and Dark, as their powers were meant to be accepted as part of themselves.

Hatoko is invited to Jurai's house to make dinner for him and his sister, but gets downhearted when Jurai decides to stay at school to talk with Tomoyo about her writing. Hatoko gets angry at Jurai when he refuses to tell her what he talked about with Tomoyo and snaps at him, going on a rant about how she just can't understand his chunibyo behavior before running off. As Jurai goes off in search for Hatoko, he worries that he might have been putting stress on her the entire time, but Tomoyo slaps some sense into him and helps him search. Meanwhile, Hatoko comes across another Chunibyo, who teaches her not to worry about not being able to understand chunibyo, before using his own power to knock Hatoko unconscious. With Jurai having no luck in finding Hatoko, Sayumi decides to bring her Root of Origin to the next stage in order to find her.

A few weeks earlier, Hajime is seen using his "Pinpoint Abyss" ability to defeat another ability user, returning him to regular life with no memory of his ability. It is revealed that this "Fairy War" between superpower humans is for the entertainment of a group of fairies, with the last eight users standing being granted a wish. One of these fairies, Litia, informs Hajime's band of ability users, Fallen Black, that an organization known as F is fighting against the war, tasking Hajime with crushing it. While Hajime is meeting up with Jurai, his second-in-command, Hitomi Saito, leads the group in attacking F's base, encountering a mysterious girl allegedly possessing an unstoppable ability, though Hajime soon explains this girl is actually a new member known as System.

While asking Jurai for some feedback on her completed novel, Tomoyo becomes embarrassed when she hears about a certain silver-wigged girl who convinced Jurai to continue his chunibyo lifestyle. Later, after the girls make Jurai to promise never to use his awakened power ever again, Hatoko helps Tomoyo with her studies. The next day, Jurai makes a promise with Chifuyu to take her to the pool during summer break, with Chifuyu learning that she may have developed feelings for him, while another male classmate, Shizumu Sagami, approaches Sayumi with the prospect of getting together with Jurai. Meanwhile, Hatoko reveals to Tomoyo that she is in love with Jurai, asking if she also feels the same.

As Jurai goes on his pool date with Chifuyu, Madoka tries to concoct a plan to get Chifuyu to hate Jurai. However, Jurai overcomes her expectations each time, leaving Madoka to become impressed by him as well. The next day, Sayumi brings Jurai to the very same pool, where Shizumu equips her with a swimsuit that would allegedly become see-through if she gets wet, but it turns out to be a normal swimsuit. Later that night, Tomoyo tries inviting Jurai to the pool, only to learn he is going on a family vacation with Hatoko.

Tomoyo recalls how she first met Jurai during her chunibyo days. Meanwhile, Hatoko tries to follow a magazine's advice to get Jurai to fall for her during their vacation, though not too much success. Upon his return, Jurai invites Tomoyo to a summer festival where they talk things out and watch the fireworks together, leading Tomoyo to realise she is also in love with Jurai. The next day, Mirei, who was captured by Naoe Hagiura the previous night, summons the literature club members together and steals Hatoko's ability, using it against her.

Mirei steals Chifuyu's ability when she uses it to protect Hatoko, before Tomoyo helps everyone to escape. Regrouping at a karaoke box, the group deduce that the Mirei they fought against was an imposter possessing her body. Jurai goes by himself to confront the imposter, tricking her into stealing his enhanced "Dark and Dark of the End", which only serves to burn its user's hand with a neverending flame that cannot be extinguished. This forces the imposter to return Mirei to her body, after which they use Chifuyu's powers to chop off the burning hands and send them to another dimension whilst Sayumi heals them. Following the incident, Tomoyo and Hatoko discuss their respective feelings for Jurai, before everyone returns to their everyday lives.