Kasa no Shita, Futari

Mio Keisuke is a high-schooler who leads a rather dull, boring life. He can't keep a girlfriend, because being a kept man's too much of a hassle, and he can't bring himself to fall in love and please his woman. Then one day he seeks shelter from a sudden downpour under the awning of an apartment owned by Yugi Kakeru, and suddenly his life isn't so dull anymore as he finds himself falling for his aloof and yet obviously lonely friend.
(Source: September Scanlations)