Theory: I think those Monsters can shapeshift to look like other people maybe? MC killed his first girlfriend Yerin (by accident) and that made Miho fall in love with him, literally obsessed with him. Since she has lots of influnce she covered up Yerin's death (or ate her) and MC lost his memories bc of the shock. And the other Monsters leave him alone bc of Miho's influnce. I don't think that MC is a Monster...
Oh that's crazy I didn't expect that Yumin literally paused her studies so she could take care of Lee Sun's father so she could be in direct contact to him??? And she knew he didn't feel that way about her from the start?? Like wow that's obsession right there. Unexpected. Somehow I thought it was all pure from her side. Love how flawed she is too. I hope she declines the friendship question like WTF. From his POV she found someone new but truth is she still loves him more than anything, clearly.
Perhaps Wooyeon developed feelings for Woojin when they were young, and that's why he was avoiding and being mean to him. I think this was brought up so Wooyeon would remember that he used to feel this way but was suppressing those feelings..