I don't like that Gotou smile and her behaviour towards Sayu, somehow look to me like she wanted to show that she is superior to Sayu(and i don't mean the question since it was a pretty normal one to ask). Sayu should know she can't stay there forever.
However i can't rly trust Gotou intentions she looks rly fishy, all that rejecting him and suddenly showing interest when MC starts to be surrounded by women. Not even sure if her being virgin is true, she could have said all of this becouse she was sure that MC is a good man and wouldn't got for sex(but guess he could also tell the truth, with her attitude i can see her being single until now). The whole explanation before that she felt it wasn't a good moment the time MC confessed is messed up, how come now was a good moment when she felt jealous. As someone mentioned before i doesn't rly look like she likes MC she liked being adored by MC and the moment she felt that MC might have a girl she suddenly went for him and confessed.
Man gonna be a hard few years until this one gonna be finished, probably a lot of drama becouse of the Gotou Sayu MC triangle, i can see Sayu escaping or leaving MC to live alone and cutting all the contact with him when MC starts dating Gotou, i can also see him realizing later that he miss the times when he lived with Sayu and realizing he loves her, that tries to find her, maybe the store gyaru gonna help him find Sayu then?