Deisui Kanojo

Nanase Izumi is unbelievably beautiful, yet so carefree and oblivious that it almost cancels out her looks. Ever since an unfortunate (and drunken) Christmas Eve meeting, a certain high school boy has found her showing up at his place unannounced. If drinking like a fish breathes water wasn't enough, she has zero sense of boundaries and is always teasing her younger neighbor-slash-unwilling host. Careless meets clueless in this rom-com about a drop-dead gorgeous but hopelessly messy home-drinker and the high school boy who keeps getting dragged into her antics.

(Source: Square Enix)