Stay ~Anata no Tonari ni~

Main character leads a quiet life until the room of the apartment he lives in gets blown up. People around him aren't able to remember him. Protagonist finds a place to live next to a wonderful girl who seems to know him, but he does not have recollections of her. There are two more girls around like that. Protagonist is a bullied nerd, but is treated like a very popular student who is good with sports. He realizes that he is in the parallel dimension and needs to adjust to this absurd state somehow. At the same time a lot of dangerous incidents start to happen around him.