Poon, alias Killer Poon, is a seasoned assassin and ex-partner of Fujiko Mine. Their alliance began within the clandestine crime syndicate "the Union," where they rose as the "Golden Couple," executing high-profile contracts with ruthless efficiency. When the syndicate accused Fujiko of betrayal and ordered her elimination, Poon, tasked as her executioner, hesitated—his emotional ties allowing her to escape, vanish, and later develop amnesia erasing her pre-Lupin III history.

Years later, their paths collide during a mission entangled with Lupin III. Employed by a new master, Poon clashes violently with Lupin’s crew. The conflict peaks when Fujiko suffers near-fatal injuries from Poon’s employer, spurring Lupin to risk everything to rescue her. This confrontation reignites buried loyalties and consequences from their syndicate past, exposing the fragile line between partnership and enmity.

Poon’s legacy lingers in the franchise, with cryptic references in spin-offs like *Is Lupin Still Burning?* and *Lupin the Third Part 5*, though specifics of his actions stay shrouded. His influence anchors Fujiko’s fractured identity and murky allegiances, mirroring the series’ core themes of betrayal and the volatile dance of trust versus ambition.