A second-year student at Minegahara High School, who is widely known to be an oddball.
The large scars on his chest are something he’d sustained when his sister Kaede suffered from puberty syndrome.
In search of Shoko Makinohara, his first love and the one who saved him, he decided to attend Minegahara High School, only to find that she was not even a student there.
After becoming involved with Mai Sakurajima, a popular actress in a class year above him, when she experienced her puberty syndrome, the two have been dating since.
A third-year student at Minegahara High School.
She could not fit in at school due to her busy career in the entertainment industry, and being treated as nonexistent at school, she started exhibiting puberty syndrome which rendered her physically transparent.
By Sakuta confessing his love to her in front of the entire school, she becomes visible to those around her again.
She has since returned from her hiatus from her acting profession, thanks to Sakuta’s encouragement. The two have also been dating.
Sakuta’s first love.
They met on Shichirigahama Beach two years ago, when Sakuta was still in middle school.
She’s the one who taught Sakuta what it means to be kind to others.
Other than her name, very little of her is known, clouding her in a veil of mystery.
She reappears just when Sakuta is stricken with grief over the loss of the Kaede of the past two years, as the actual Kaede regains her memory.
A middle school girl who looks just like and shares the exact same name as Sakuta’s first love.
She was holding her umbrella over an abandoned cat to shield him from the rain when Sakuta and Mai encounter her on their way home.
As Sakuta ends up taking in the cat, Hayate, she begins to frequently visit them as his place.
She admires Sakuta.
A first-year student at Minegahara High School.
Her relationship with Sakuta began when they literally kicked each other’s butts.
Because it has always been her number one priority to read the room and to accommodate to everyone around her, she experienced puberty syndrome when an upperclassman that her friend has a crush on confesses his feelings to her.
As a result, she must repeat the day over and over again until it ends with her desired outcome, dragging Sakuta along through this ordeal.
Now, she and Sakuta have become close as senpai and kouhai, being able to freely talk just about anything with each other.
A second-year student at Minegahara High School and a member of the Science Club.
When Sakuta and Kunimi, two of her very few friends, each began dating their girlfriends, she was hit by a sense of alienation that instigated her self-sabotaging use of social media.
This resulted in her puberty syndrome where a clone of her with an opposite personality appeared.
Although she always seems annoyed whenever Sakuta comes to her for advice on puberty syndrome, she still offers him her best advice.
Mai’s half-sister, related through her father, and a member of the idol group “Sweet Bullet.”
She had developed an inferiority complex as she was constantly compared to Mai growing up, which led to her puberty syndrome where Mai and her bodies ended up being switched.
The sisters now live together at Mai's place, and Nodoka often gets in Sakuta’s way on purpose. She has also become close with Kaede, whom she and Mai care very much about.
Sakuta’s younger sister.
She was the victim of online bullying at her previous school, which was at the root of her puberty syndrome that caused any emotional distress to become physical injuries.
As a result of the extreme stress she underwent, she suffered from amnesia. She developed a persona of another Kaede, who was unable to leave the house at all for the past two years.
But thanks to ceaseless efforts made by the Kaede, she has regained her memory and is now working hard with Sakuta to return to school.