Looking for a specific hentai manga that was on Fakku

On the cover, the girl had pink short hair. It was about this guy who found a girl washed up on the beach and they eventually have sex. The guy realises the girl seems different or something when she starts having sex or something. Then when the guy came, he just fainted if I recall and the girl somehow gains energy by having sex. Later either the girl decided to move in to his house where his mother also lives. The mother was cool about it and was even ok with them having sex.

This manga was on Fakku a long time ago before Fakku changed to having to buy all manga to access it. If anyone knows the title please tell me.