Sora and Tatsuki are stepbrothers (not blood related) whose parents died in an accident. Since then the elder brother, Sora Mukaihara has brought up the younger one, Tatsuki Mukaihara. Now Sora is a very popular mystery writer. Tatsuki who has moved out on his own, is now an editor of a women's magazine. However Sora can't stand being alone and spends all his time at Tatsuki's. Tatsuki feels guilty because he can't stop himself from loving Sora and decides to live a solitary life. Then Sora asks to have Tatsuki assigned as his editor when he agrees to do a series of interviews for Tatsuki's magazine.

(From mangaupdates.com)