Tomariba

Suddenly, various girls and young women he has never met before begin to arrive unannounced and uninvited at the his doorstep, asking for supper and to spend the night, and not taking no for an answer. Afterwards, they nonchalantly proceed to undress and ask him to have sex with him, disappearing in the night and leaving him to wake up to a thank-you card in the morning.

They divulge no personal information and don't even give him so much as a name. However, the do occasionally mention having had certain expectations from what they were "told."

Just what exactly is going on?

Included one-shot:
Pet