Due to an accident that happened in the apartment a girl was supposed to move into, she has to temporarily move in with the landlord's son along with two other girls.
They all attend the same high school.

I can't remember the name of the manga either, but I think I remember it, its the one where the girl moves in with the land lords son, but her and the two other girls don't get along initially, but then theres a blackout etc.

Feed your head.

Okay I remembered now; It's called Kono Ie de Kimi to.