Neat fact I just learned, due to the way the Japanese school system separates student cohorts, Komichi is the probably the oldest in the class (DOB:04/04) while Erika is one of, or even THE youngest (DOB:03/23).
This also means we can be pretty sure, unless their school is unusual, that Komichi...
There's no way to convince me that this ends on heartbreak for Kurohime. I do, however, think that her and Rin need at least one more interaction for a poly end to make sense.