|Relatives||Nephew - Makoto Kubota|
|Manga||Wild Adapter (Manga) Vol. 1 Ch. 2|
|Anime||Wild Adapter (OVA) Ep. 2|
Kasai Keiichirou（葛西） is a detective and the uncle of Kubota. He was assign to investigate the mystery drug W.A. along with his fellow detectives, Araki and Hasebe. He gives Kubota some hint information about Wild Adapter and helps him in various ways.
His purpose about his responsibilities about Makoto's upbringing is somewhat odd. Just like his nephew, he smokes and a bit of a crooked cop but not to mention that his an excellent player in mahjong. He's also a good cook although the only thing that he knows was preparing and cooking curry. He is somewhat cool most of the time and gets serious when it comes to his job at investigating victims of W.A. He's also a strict and overprotective of Makoto since he is the only relative of him who looks after him from time to time. He even gave Makoto an advice not to get near of Sanada.
Based on his looks, Kasai appears to be a middle aged man. He sometimes has some band aid on his face. He has a blond-grey spiky messy hair and always sees him with a cigarette.
Kubota Makoto - Makoto was his nephew. In Dice 46 (Dice 42 in Ichijinsha), he was narrating some story about how he met his sister's only son. Makoto was around thirteen and a freshmen in high school when Kasai pick him up and take charge the responsibility as a parent and guardian to his nephew after his sister died. He says that he can sees any traces of his sister in his nephew. He brought Makoto to his place and he stayed some time. Kasai doesnt know how to act as a relative to his nephew and soon he always let his nephew do his own way to the point that one time, Makoto himself said that whatever he says doesnt reach to him. He later then took an interest to Makoto and occasionally took his nephew to Mahjong Parlors. He was proud of his nephew for being a fast learner. Kasai is actually overprotective of him and would slap him if needed. He keeps telling advices to Makoto not to get involve in problems.