Obbligato

The protagonist, Kazuki Ogata, was in love with a certain girl. She was a girl of exceptional beauty with long, striking black hair, Chisae Hisaki. She was often quiet and expressionless, making it hard to discern her thoughts, but Kazuki was drawn to the mysterious charm she possessed. After much contemplation, Kazuki decided to confess his feelings to her. And to his delight, Chisae accepted his feelings, and the two of them became a couple.

Kazuki was overjoyed to be with Chisae, but later on, he would hear some shocking rumors about her. It was a well-known rumor at Sakura Seiki Academy. Chisae Hisaki was rumored to be the "girl who sleeps with anyone."

However, Kazuki wondered if he could still love her. And if he could ever open her heart...

[From dlsite]