Futari no Kimochi

A third-year high school student named Kan Okada is preparing for university entrance exams when he reunites with Fuyumi, his brother's ex-wife, at their shared prep school after three years apart. One evening, after playing tennis, Kan kisses Fuyumi upon returning home. His brother happens to be present and witnesses the incident, raising questions about how this will affect Kan's relationship with him.