Koi Bride (鯉女房, Koi Nyōbō, lit. "Koi Wife") is an indoor fishing pond located on Shichifuku Street, Kamurocho. It serves as a front for the underground casino L'amant.
Takayuki Yagami and Masaharu Kaito first come here in Chapter 2 to find a police officer who gives out info for cash. They are looking for the mysterious officer when a gang of youths come in and fight the pair. After this, the nonchalant-looking owner reveals that the fight was a test: the real action is taking place in the basement, where there is an underground casino called L'Amant.