@Mikhail, I could tell of
@HenrykDodwel, because he used “the m.c.” to refer to one of the two main characters who's arguably the deuteragonist since most of the story is from Nanami's perspective and focuses on Nanami's home situation — if one of them is to be designated the main character and the other secondary, then Nanami is definitely the main character.
However that shall never stop a self-inserter, who shall always consider his self-insert to be the “main character”, implausible it be.