Mai Otohime, who excels in all kinds of marine sports and possesses ocean knowledge that rivals that of experts, also aims for the Mitsuoka duel. However, Mai's target is Thirteen. Noren challenges her to a duel. Meanwhile, as Thirteen and his friends prepare for the duel, they have a three-way meeting. As each of them grapples with their own future, Thirteen also experiences a change of heart after his school life and encounters with his friends. 

Thirteen was enjoying a peaceful school life, but then Kazuma and Eiji transfer in, creating an unusual situation where four assassins have infiltrated the same middle school. Meanwhile, the Home Economics Club is holding a ramen-making championship. Thirteen, who is on the same team as Noren, saves a girl from being hit by a truck while investigating ramen. Who is this girl...?

Under hypnosis, Noren falls in love with Juzo and aggressively pursues him. However, when Juzo gently rejects her, she attempts to jump off the roof. According to Kazuma, he had cast a hypnotic spell that would make her fall in love with the first person she sees when she wakes up, and a "heavy" one at that. Determined to break the spell, Juzo heads to the amusement park where he is meeting Kazuma, and ends up riding the Ferris wheel with Noren. Then, the two of them seem to be in a rather romantic mood...!?

Thirteen rushes towards Noren. Meanwhile, Tenma and Eiji are engaged in an epic battle of soccer versus bomb golf. Tenma tries to put an end to his fight with Eiji using a technique he developed during practice! And after a fierce battle with Kazuma and Eiji, Noren, who had been unconscious, wakes up. What he sees reflected in his eyes is...

Kazuma wields powerful hypnosis, while Eiji launches a fierce attack with explosive golf balls. They, too, are assassins pursuing the secrets of Mitsuoka Pharmaceuticals. Thirteen struggles against Kazuma, who uses hypnosis to control and attack ordinary people. Furthermore, Kazuma casts a hypnotic spell on Noren. Thirteen rushes to Noren's side to rescue him, but...

Juzo and Noren end up on a double date with Chisato and Tenma. The four enjoy shopping and lunch, but the moment the movie starts, Juzo mysteriously reverts to his adult body! He rushes to the restroom, only for Noren to be kidnapped again. Chasing the culprit's car to a stadium, Juzo and Tenma face Kazuma and Eiji Rindou, assassin brothers from the industry's top organization, JARDIN.

Juzo and Tenma's futsal showdown begins. With his astonishing physical ability, Tenma overwhelms the Home Ec Club team of Juzo, Shin, and Kito. Sensing that Juzo is no ordinary opponent, Tenma drops the handicap and starts playing for real. Juzo and the others fight desperately to keep up with Tenma's dominant performance, but how will the match end?

Juzo and the Home Ec Club bring rice balls to the baseball team, where they meet elite ""Unicorn"" Tenma Tendo. An ace in baseball, soccer, and basketball, Tenma boasts that he'll become a "triple threat superhuman." When he challenges Juzo to futsal simply because he's "in the way" and mocks the Home Ec Club as a pointless play club, Juzo accepts.

Juzo is still uneasy about pretending to date Noren. But then Shin Kohazame, a middle-school assassin from the Chinese underworld group Yuigan, transfers into her school to become her fiancé and claim Mitsuoka Pharmaceutical's research and new drug. Shin challenges Noren's "boyfriend" Juzo to a duel, and their battle begins!

When Juzo falls behind in school, his classmate Ryo Shiraishi starts tutoring him. He also joins the Home Ec Club run by Ryo's older sister, Chisato. Noren joins too, hoping it'll help with making ramen. Then, after Mitsuoka Pharma announces that whoever marries Noren will inherit the company, a cornered Noren blurts out something completely unexpected!

The wasp that stung Juzo was created by Mitsuoka Pharmaceuticals, and it turns out that the daughter of the company's president, Noren Mitsuoka, is in Juzo's class. Beautiful, brilliant, and athletic, she's untouchable. Hoping she may hold a clue to restoring his original body, Juzo discovers that Noren works at a ramen shop and starts forming a connection with her. But then, Noren is abducted...

At 39, legendary hitman Juzo Ogami is stung by a mysterious wasp-like bioweapon and passes out. When he wakes up in Z.O.O.'s lab, he's shocked to find himself in the body of a middle schooler. His next mission: infiltrate a middle school. Though reluctant at first, Ogami unexpectedly discovers the joy of learning, until a suspicious intruder storms the school.