One Room, Hiatari Futsuu, Tenshi-tsuki.

Summary:

Shintarou Tokumitsu is a high schooler living all alone, but things take an unexpected turn when a girl named Towa shows up on his balcony! Not only is she incredibly pure and sweet, but there's something different about her—something...divine. Just who is Shintarou's new roommate, and what adorable high jinks lie in store?!