Gunslinger

Known as "Gunslinger who never lands a hit", he is a skilled gunslinger who utilizes catnip as a weapon agaisnt the cats. First shown when he showed up outside a castle as a reinforcement.
He alongside Tsutsumi and Last Samurai with very few others are forced to go somewhere after being overran, where they eventually arrived in the Citadel.
The Gunslinger is hired by Tsutsumi in a wild west town as shown in one of her flashbacks.

His outfit is that of a gunslinger cowboy, and he wields 2 pink powder sprinkler gun which fires a catnip powder in order to get the attacking cats to sleep.

He also appears to have a cat archnemesis, Diamond Claw.
He worked alongside the Last Samurai.
The Gunslinger has a singing and musical talent, as shown when he played a guitar alone singing about cats.

(Source: Nyaight of Living Cats Anime EP9 and EP10)