ハーレム天国だと思ったらヤンデレ地獄だった。

The progatonist, Kisaragi Yuuya, is the deputy head of the local high school history research club, and the student council has spoken: show off something to the next cultural festival or kiss your club goodbye.

As such, Yuuya and his three fellow club members try to create a mascot character, Izaemon, to amass appeal for the club.

However what follows was something that no one could have ever predicted...