The April issue of Shueisha's Bessatsu Margaret magazine revealed on Monday that Minami Mizuno will launch a side-story manga for her Rainbow Days manga in the magazine's August issue on July 13. The new manga will be on an irregular serialization schedule. The main Rainbow Days manga published its final chapter on Monday.

Rainbow Days centers on a group of four male high school students who are close friends: Natsuki, Tomoya, Keiichi, and Tsuyoshi. The four boys have no club activities, and they hurry through their studies so they can spend their days having fun. Their main topic of interest: love. Natsuki has an unrequited crush on Anna, a girl from another class, and his friends keep meddling in their relationship.

Mizuno launched the manga in the February 2012 issue of Bessatsu Margaret. Shueisha published the 14th compiled book volume in December. The manga inspired a drama CD that Shueisha bundled with a limited edition of the seventh volume in October 2014. The manga then inspired a television anime that premiered in January 2016. Funimation streamed the anime as it aired in Japan. The manga's 13th volume then bundled an original anime DVD last September.