Based on the erotic game by Anim.

One day, when Koichi was on a crowded train, a girl in front of him suddenly cried out, "He's a train molester!" "What!? No, I didn't do that!" He was mistakenly arrested for train molestation. Two years later, Koichi is now on a train to take revenge on that girl, "I'll do it...."

(Source: ErogeShop)