So I don't know quite how all the pieces fit together... but I think what is clear is that Michi at one point was really close to Honami, which explains Honami's fixation on her, somehow through either trauma repression or some kind of Supernatural Shennanigans, Michi doesn't remember that, given the childlike manifestation of Michi, the idol candidate from a flashback in the latest chapter with dark hair and a similar name who entered auditions alongside Honami, and how supernatural phenomena swirl around the pair, there's a lot of possibilities but little certainty.