Strobe Edge by Ryuichi Hiroki

6.10

Ninako Kinoshita has never been in love until an encounter with the school's most popular boy, Ren Ichinose, leads the two to befriending each other. Ren's patient and kind personality is a far cry from his unapproachable idol status at school, and soon Ninako falls in love with him. However, she must cope with the fact that he already has a long-time girlfriend.