You Are My Regret, Vol. 2 (novel)

Yuzuru has begun to mend things with his ex-girlfriend Ai, finally overcoming his long-held regret. But his relief proves short-lived when fellow literature club member Kaoru stops coming to school. Yuzuru, who cares for her and knows something about her situation, tries his best to help, but she refuses him at every turn. As loneliness and a new regret take root in Kaoru's heart, how will her relationship with Yuzuru change?