Monsters, called "Breed", threaten the people of Japan. Tatsuhiko Shibafuji, the proprietor and sole employee of the Shibafuji Detective Agency, possesses great powers that can be used against the "Breed." However, this guy only accepts those cases that attract him. Due to his nighttime activities, people within his industry call him the "Night Walker."
Tatsuhiko receives a request from a private sponsor, Yayoi Matsunaga, who is an inspector on the police force. Our hero sets out to inspect a suspiciously related incident at Saint Michael All-Girls Institute. He comes in contact with one of the friends of the victim, Kazumi Asano. Our hero and Riho Yamazaki find a secret underground room beneath the chapel. Here, they find a pendant, which had belonged to Kazumi. The situation is much more serious that he had expected.
This AVG is an orthodox command-selection game. A player searches for clues by traveling to different places, meeting different people, and obtaining various items. Throughout this detective story, a player will come upon many obstructions that will have to be cleared in order to solve the case.