Synopsis
Business is slow at the Ootsuji Detective Agency. Soutarou and his young partner Saki accept any case that comes their way, even one that seems far more dangerous than it is worth. The city is in the midst of festival season, but away from public view, a string of strange disappearances has been happening. A newspaper reporter hires Soutarou to look into it, hinting that the answer may lie in the Dark—the city's lawless, chaotic underground, a maze of physical, social, and moral decay. Soutarou passes the job to Saki, but soon regrets it when the boy vanishes as well. Now Soutarou has no choice but to descend into the Dark himself and face its shady subterranean inhabitants, including the vicious Laughing Masks gang and a rogue police squad operating the fearsome armored train Demon 463!