Nishuume no Koi

Yamamoto was in love with Minowa, but never confessed to him. After meeting again at a high school reunion, they get drunk and go to a love hotel in the spur of the moment. But when Yamamoto wakes up, he finds himself in his old home, ten years in the past! While he needs to find a way to get back to the present, Yamamoto also wants to lay his regrets to rest. "This time, I'll say what I couldn't say on the day of the school festival..."

(Source: East Press, translated)