University student Hirose Kiyotaka finds a love letter tucked into the pages of a borrowed book. While attempting to return the letter, he encounters the charismatic Hanashiro Seiji and quickly becomes involved with him. As their tentative relationship develops, however, he finds himself wondering how serious Hanashiro's feelings for him really are. Meanwhile, the letter falls into the hands of Hanashiro's colleague Sawa Jinichiro, who entraps its writer, Arihara Mineo. Sawa's actions are seemingly ruthless, but his true motives regarding Arihara are far from clear.

This series is the sequel to and a continuation in the Sakae Kusama's Lost Letters series.