Neconeco Darling

Sai is a member of the school's disciplinary committee who is respected by his juniors and relied on by his schoolmates. He really hates Zenji who is only late to school on weeks that Sai is on duty. Sai used to be close with Zenji in grade school but they grew apart from each other because of something that had happened then. Despite that, Zenji has, for some reason, started trying to get close to him? (Source: Libre, translated)