The story starts with Mita, a second year middle school student, getting attacked with a kitchen knife by his classmate Fuyumura. While Mita couldn't make sense of the situation at first, he gradually came to believe that Fuyumura's actions were just mean acts stemming off from the latter having a peculiar puberty phase.

But that was all actually a misunderstanding. Fuyumura is seriously questioning if Mita is actually the descendant of a certain family...

[Source: MU]