Read the description of that race:
Foul (外道, Gedō, lit. Heretical Doctrine) is a race of demons in the Shin Megami Tensei series. Generally the demons of this race can be divided into 2 category. The first being the Slime and akin such as Ooze. The second group contains the ghosty beings born from various urban legend.
Yakuza isn't an actual human gang member, but rather a representation of how humanity as a collective has romanticized people belonging to that group.
Like with Hell Rider, who is just an infamous biker gang's logo(the Hell's Angels specifically, which is what its name is in the Japanese games), and Mothman, who is kind of a big-foot situation, entities infused into the popular consciousness can become demons.