Youta, a band member, is asked to write the theme song for a romance variety TV show, but the producer says, “It doesn’t convey the feelings of love,” and makes him rewrite it.
This was obvious, as Youta’s relationships with women had only amounted to “having some fun, then cutting them off,” and had never felt “love” before.

“If only I could, just once, love someone…”

When he was stuck while looking for inspiration for that kind of song, he came back home one night to his roommate Mahito, a resident doctor, masturbating and calling his name…?!

Youta wants Mahito to write about his love for him in his notebook to use as material for the song, but…

A BL story begins between Calculating x Pure Love.