Breath: Toiki wa Akaneiro

The protagonist of the story is a 21-year old Hibiki Akimine who, after finishing high-school, didn't have any plans for the future which resulted in him doing various depressing part-time jobs. But the luck was smiling down on him and something new was about to enter his life. One day, while walking through town, he noticed a girl in trouble and saved her from an unknown man. Her name was Akane Nagumo, and she is a number one idol. He didn't know anything about her, but reluctantly, offered to help hide her at his place for the moment. Thus, the strange new cohabitation of Hibiki and Akane began... something that could turn his life upside down and pull him out of his brooding and lack of optimism.

[From Mobygames]