From Phoenix Serenade Scans:

Sakura Yuki and his neighbor, Momo were separated during Yuki's third year of high school because of a certain incident. Yuki thought that they weren't really friends considering that there was a 12-year age gap between him and young Momo. But 10 years later, Momo, now a high school student, becomes Yuki's neighbor once again. Momo is eager to be friends again but Yuki feels differently as he remembers things he buried in his heart long ago. Momo and Yuki battle their past and present to slowly become closer than ever.