Wong, whose full name is Xianweng Ni, is a 13-year-old orphan living in Hong Kong. He resides on a boat, identifying as one of the "Boat People," and cannot recall his parents' appearance. As the youngest member of Wuying Ren's gang, the Heavens, Wong engages in pickpocketing and theft targeting tourists, displaying skill in deception and lock-picking. He steals Ryo Hazuki's bag upon Ryo's arrival but subsequently forms a bond with him, showing care and loyalty through repeated assistance.

Wong helps Ryo locate stolen belongings and provides information about the Come Over Guest House. He offers Ryo temporary shelter on his boat and gives him the Heavens Zippo lighter to access Beverly Hills Wharf. Later in Kowloon, Wong aids Ryo and Ren by picking their handcuff locks and provides a map revealing Yuanda Zhu's location in the Yellow Head Building. Wong faces capture by Dou Niu but is rescued by Ryo.

Initially mischievous and unapologetic about theft, Wong evolves to show genuine concern for others, viewing Ryo as an older brother. In the anime, he expresses a desire to stop stealing for survival, ultimately starting a small business selling bananas. This entrepreneurial step marks his aspiration for a legitimate livelihood within his harsh reality.