S, Vol. 1 (Sエス #1)
Saki Aida, Chiharu Nara

Welcome to Shinjuku district's Kabukicho, Japan's red light district. Here, the streets are dotted with bars, pachinko parlors, and "love hotels," which cater to all sexes and sexual orientations. These are the streets which Detective Masaki Shiiba must patrol.
A recent rise in gun crimes forces Shiiba to go undercover and work with an "S" or spy, a member of a crime organization tasked to hand over information in exchange for special favors. Shiiba's S is a man from the influential Matsukura Group, and someone who seems to have developed a fondness for Shiiba.
But when the detective gets a mysterious call warning him about his S, seeds of doubt are planted. If he can't trust his S, who can he trust?