My theory from reading this is they were in a relationship in high school some kid found out about them because they were being careless thus the rumors then for some reason mc blames ml in the name of immaturity and self-preservation. I also think pado is kinda trying to entrap mc like 'I want u so I'm going to make u can't live without me' type thing, it's either that or the 'I'm gonna make u love me then break u like u broke me' type of vibe got this idea from the sister saying he's Obsessive plus her little flashback about when she first met him. The timeline thing I'm really curious about because when we first see him it's his 4th time trying to get into the uni but after that it's his 2nd try(hmm) plus he knows way more ppl,etc