Mako was a minor antagonist in Volume 5.
He was an enormous, largely muscular man who apparently artifically carved his teeth down to a fine point, weaponizing them. He was first alluded to in V5C1's bonus scene, where it was revealed that he killed a hustler by completely eating off his neck. In the next chapter, it was revealed that he had hired 2 goon men -- Bennie P (a teenager known by Ken since childhood) and Shakes (a mentally unstable man) -- to help him intimidate a store owner who he also ate the neck of, but the neck was also eaten off.
Diego Hernandez informed Ken that Mako's 3rd target was in a warehouse; unfortunately, by the time he and Samuel Martinez got there, the victim was found. A shootout between Ken, Martinez, Bennie, Shakes and Mako occurred. Bennie and Shakes were shot in the process, with Shakes being fatally injured, but Mako was arrested.
Just as Mako was taken outside, he was executed by a masked vigilante dubbing himself the "Hand of Justice".