Thinking about this flashback and multiple things that happens, we can probably see how Mikoto was basically lead to being bullied during her first year. Because Kuroko mentioned that Mikoto was being bullied by her last roommate and I feel like the school probably knew about the bullying and allowed the room swap to essentially deal with it a bit. Also when Misaki removed Kuroko's memory of Mikoto, Kuroko seemed to have shown a bit of disdain towards her, like there might've been rumors about how Mikoto looks down on (doesn't care) about those on the lower levels like depicted here. Mikoto was also shown to not really have many friends in the school and most of the ones she became friendly with are basically those on a grade below her's. She also goes to extreme lengths for these friends so I wonder if there's also a reason for that as well. Many theories going through my head rn and they all connect somehow to me, so i'm pretty excited for this arc xD