Bunny girls do not live in libraries. This is simply common sense. And yet, that's exactly where Sakuta runs into one in the wild. Sakuta launches an investigation to figure out what's making this bunny girl invisible to everyone around them.
"Today...is yesterday?"
Sakuta may have cured Mai's Adolescence Syndrome in the nick of time, but now he faces a no-less-harrowing task: convincing her to officially date him. After managing to win that round of verbal fencing, he gets some well-deserved rest...only to wake up "yesterday," with all his progress reset. This inexplicable phenomenon seems to be caused by Tomoe Koga--the self-righteous yet self-conscious schoolgirl who offered up her own butt to be kicked after mistakenly assaulting Sakuta's--and the only cure is to...pretend to be her boyfriend?!