Kitajima Kei (34) A highly educated elite lawyer. He is a brilliant man who can handle anything with aplomb and dexterity...except love. Kei has had a crush on his best friend since college for 15 years. He is not good at socializing, but his best friend's hand leads hiim out, He just loved the soft, low voice of his best friend. But when his best friend, Yusuke, got married, he put a lid on his feelings. While keeping them hidden, a younger tattooed man with a voice similar to Yusuke's asked him out. Kei is shaken by the proposal of a “substitute”...

[---There's a dream I've been having for a long time, a dream of unending regret.] This spring, Asahi, a new member of the workforce, finally achieved his dream of becoming a teacher. He was supposed to take a job at his alma mater and start a new chapter as a new teacher... but his mentor during his training period turned out to be his high school teacher and first love, Chiba Naoya! Chiba is delighted by the chance reunion, but for Asahi, his er first love is a "symbol of regret"...? A senior teacher and a new teacher relive their unfulfilled first love. A painful, lingering sadness builds up in this reunion school office romance.