The story behind Waru is that one day, while taking a train, you, Honda, met a girl named Amano. On the crowded train, she lifted up her cloth on her own initiative and allows you to touch her breast. At first, you are surprised by her action. However, you soon started to enjoy the "wicked play" as Amano unlocks the long forgotten "wicked play" inside you. Once again, you start to haunt lonely girls on the train as your target of the "wicked play."

[from Anime Densetsu]