Tonari no Onee-san

Haunted by the memory of his ideal woman, Masahiko is determined not to lose his virginity until he finds her again. Too bad his memory sucks and he can`t remember who she is. While Masahiko is dreaming of his mystery woman, he may not have a choice in waiting for her much longer! It seems that everyone wants a piece of him lately. At work, his sex-starved boss is looking for a little action while her husband is out of town. At home, a very buxom childhood friend moves in and leaves him drooling. At college, he`s become the target of both his professor and a sly sexy student stalker who manages to pop up in the most unusual places! To top it off, Asuka, one of his neighbors, is secretly harboring her own fantasies about him! With this amount of sexual frustration swirling around him, can he possibly manage to hold out for the girl of his dreams.

(Source: AniDB)