By chance, Fujiki Seigo, a college math major, encounters a brilliant young man named Ichinose Jin while doing his laundry. Despite Sei's initial reluctance, Jin persuades him to provide math tutoring during his spare time. However, Sei's childhood friend Aki is less thrilled with the development. When the two of them express their love for Sei simultaneously, what decision will Sei, who is grappling with his emotions, make? It is worth noting that the total number of chapters includes an "extra" chapter.