The morning after a class reunion, Uichirou wakes up in bed with a stranger. He's told he clung to the man the night before, crying, and called him "senpai." The two form an arrangement as sex friends, but feelings begin to develop between them.
Senpai was an absent character but everpresent throughout the story. I wondered if we would get to meet this person, but it didn't matter who he was or where he is now. Uichirou needed to move on from their past. I was a little frustrated with the late-game communication issues between the two main characters, but the reveal of the chief's wife (Mama) was delightful.
Yoru ga Aketemo