Ikuro Makino, a first-year student at Misoragaoka Junior High School, decides to confess his feelings to Yoshie Okahara, who is in the same class as him, and gives Yoshie a slip of paper with a note asking him to come to the back of her court after school. Immediately after Yoshie blushes at her, a huge explosion occurs in the classroom.Yoshie is taken to the police station for questioning, where she learns that she is the cause of the explosion. . Yoshie is troubled by the fact that she has injured Ikurou, but in order to repay his feelings for being kind to her, she escapes from detention during the questioning and goes to Ikurou. He literally runs towards the back of the school court where he is waiting.

The two finally become lovers, but incidents keep happening around them. Even after being promoted to Class 2F, the turmoil continues to grow with the appearance of the mysterious transfer student Sonoko Sonobe and the popular talent Kohei Kamisaka. However, they overcome these difficulties with their innate "carefree spirit".