Keiichirou Kasai

Оригінальне ім’я: 葛西蛍一郎

Kasai is Kubota's uncle and a detective. He gives Kubota information regarding W·A and helps him out in various ways, like letting Kubota off the hook when he turns up at the scenes of assorted murders or gang turf-wars. He is very concerned about his nephew, but his advice does not always get across to Kubota.