Kamisama Onegai!

Life was a mundane chore for student council member Hasumi Ryou, until he picked up a charm on the floor. Suddenly a junior high-school student with bad grades appears in his room calling him Kami-sama and asks for help to pass her high school entrance exam. Not to mention that it doesn't make sense that his room changes into hers everyday after school, Ryou abandons all logic and decides to go with the flow, his heart touched by the earnest desire of the girl who wants to graduate to high school.

(Source: Shoujo Crusade)