A second-year at Minegahara High School and an eccentric person in school. He has a huge scar on his chest when his sister, Kaede, was suffering from the Puberty Syndrome. He enrolled in Minegahara in search of Shoko Makinohara, his first love, but she was no longer there. He is now going out with Mai Sakurajima.

A third-year at Minegahara High School. She developed the Puberty Syndrome as a result of her busy schedule as an actress. She never made any friends and was constantly ignored, which eventually led to her fading from existence. After witnessing Sakuta's love confession in front of the whole school, people became aware of her existence.

Sakuta's first love. She first met Sakuta two years ago when he was still in middle school, at Shichirigahama Beach. She was the one who taught Sakuta what "kindness" was. A mysterious girl whom Sakuta knows nothing about, but her name. She appears before a devastated Sakuta once again after "Kaede" returned to her "old self".

A middle school student with the exact same name and face as Sakuta's first love. Sakuta and Mai first encountered her on a rainy day, when she offered her umbrella to an abandoned kitten. After she leaves the abandoned kitten—Hayate—in Sakuta's care, she has been visiting every now and then. She is deeply attracted to Sakuta.

A second-year and sole Science Club member in Minegahara High School. After two of her closest friends—Sakuta and Kunimi—started dating, she started feeling lonely and engaged in self-harm activities on social media. As a result, she developed the Puberty Syndrome whereby one that is a total opposite of herself- appears.

A first-year in Minegahara High School. She 's Sakuta's butt-kicking buddy. She was obsessed with reading the mood and fitting in with the people around her. However, after a confession from her close friend's crush, she developed the Puberty Syndrome. With Sakuta involved, Tomoe repeated the fateful day until she reached her desired outcome.

Mai's step-sister with a different mother. She is a member of an idol group Sweet Bullet. She developed a complex after being constantly compared with Mai as a child. As a result of the complex, Nodoka developed the Puberty Syndrome where she swapped appearances with Mai. She now lives with Mai and often disturbs Sakuta.

Sakuta's younger sister. She suffered from the Puberty Syndrome whereby her whole body was incised with countless mental scars from cyber-bullying in her previous school. As a result of mental stress, she lost her memories and lived in seclusion as "Kaede"—a split personality.