Yè Ziying is a streetwise youth aged 12-14 during the main events. He lives in Shanghai with his father, Yè, a former Qing Bang triad member severely injured by torture from the rival Hong Hua Hui gang. Both assist Kenshiro Kasumi upon his return to Shanghai.

Ziying first meets Kenshiro when Kenshiro saves him from Hong Hua Hui members killing a minor drug dealer. After this rescue, Ziying impulsively steals Kenshiro's bag but brings it to his heavily bandaged father, revealing their prior connection to Kenshiro, who is Yè's old acquaintance.

Ziying witnesses the Hong Hua Hui humiliate his father and joins Kenshiro's retaliation. He accompanies Kenshiro and his father into the Hong Hua Hui's "Great New World" building, home to the brutal "Game of Death" fighting arena. This arena has killed many Qing Bang members, including Yè's brother, Zhang. Ziying observes Kenshiro enter the fights disguised as his bandaged father to challenge the Hong Hua Hui's champions.

His role mirrors Bat from "Fist of the North Star," serving as Kenshiro's youthful companion and supporter during the Shanghai conflict. Ziying also appears in the "Regenesis" storyline.