Wanko to Kurasou follows the life of Yuuichi, a college student, over several months. He teaches a cram school and lives alone. He was an orphan when young, and was adopted by an escort. He spent many years growing up in brothels, and eventually entered the industry himself. The experiences he had when maturing resulted in him becoming cold and cynical towards the themes of love and attachment.
It is set in Japan, in a world parallel to reality, with the exception being that there exist a variety of pets known as Anthropoid animals. These pets include cats, dogs and birds, though birds never make appearances in the game. They have human form (ears and tails seem to be the only outward changes in appearance,) show some intelligence, and are even allowed to hold special jobs. However, they still retain much of their animal instincts, most notably the urge to mate during the Spring and Fall seasons.
The game has two routes, each focusing primarily on one or two characters: The Nadeshiko route, and the Risa route. Both routes, however, included development of other characters. The Nadeshiko route revolves around the owner of a nearby pet-store, Nadeshiko, and her pet anthropoid dog, Kotarou. This route was translated before the Risa route, despite the lower popularity of Nadeshiko, possibly because of the greater amount of ero-scenes in her route. Yuuichi eventually ends up in a relationship with Nadeshiko, but is unable to ultimately commit. The Risa route revolves more primarily around Risa, Mikan and Silvie, showing more character development, most notably with Risa.