Uchi ni Oide yo

Natsuki cannot fall asleep unless he tires himself out through sex, so he picks partners with no strings attached to help him out. One rainy day, he comes across a handsome guy waiting in the rain at the entrance to his building and takes him home. With one condition, they begin to live together in Natsuki's apartment.

(Source: Renta)

Included one-shots:
Hatsukoigokoro (First Love), Irokoigokoro (Intense Love), Kore Bakari wa Shikatanai (This Just Can't Be Helped)