Wen was a victim of the Astral Gate accident that caused his body to stop aging and rendered him virtually immortal. He awoke to realize his parents were dead and he was the only survivor of the accident. In order to keep his condition a secret, he would kidnap older men, render them paralyzed, and pretend that they were his father or guardian. Wen became a gifted harmonica player on Mars and played in a nightclub for many nights.
Wen was eventually discovered and subjected to experiments in a secret facility. The facility became known to the Self Defense Volunteer Squad and two of their agents, Zebra and Giraffe, attempted to reclaim it. Zebra was abducted a few days later and became Wen's cover for the next ten years.
Giraffe continued to search for Zebra, and eventually found him and Wen in a hotel. Giraffe threatened Wen with a gem that could undo the effects that kept Wen immortal. Wen simply shot Giraffe and he went through the window. Unbeknownst to Wen, Giraffe had been followed by Spike Spiegel, who was outside in his ship. Wen looked out the window to see Spike save Giraffe from falling, but Wen knew Giraffe would die from his injury.
Wen led Spike into a trap in a warehouse later and questioned him about the gem. When Spike claimed not to have it, Wen started a shoot-out in which he disposed of Zebra, but was also shot in the head. However, he still escaped. He later stole a taxi cab to leave to the outskirts of the city. However, Spike followed and forced the cab to hit a gas station, exploding. Wen decided to play with Spike a bit, shooting very near him, however, he didn't realize Spike's bullet had the gem embedded in it. Wen was killed when Spike hit him in the head, causing him to age rapidly. 
Wen's age is inferred from the note that the gate accident took place in 2021, and Wen was 12 at the time.