Four guys in a friend group, each chasing different girls, and somehow the real story is just them being terrible at romance together. The OAD strips away the manga's ability to hide in panels and forces the comedy to live or die on timing, voice work, and the specific chemistry of these four idiots trying to give each other advice they don't follow. It's the kind of thing that only works if you've already let these characters into your head through the manga, which is exactly why they bundled it with volume 13, this isn't an entry point, it's a reward for people who already know why watching four boys fumble through crushes matters more than whether any of them actually win.

Rainbow Days OAD is a single-episode original animation from 2016, adapted from the shoujo manga series written and illustrated by Mizuno Minami. The episode was released packaged with the limited edition of the manga's 13th volume. As a comedy and romance with a slice-of-life focus, it offers a lighthearted bonus story alongside the printed series.