Starting with the Different Colored Gas Bomb, he became the Poison Master.

Ye Kai unexpectedly transmigrates to a world of urban Pokémon. He discovers that this is a world where Pokémon are divided into different ranks. Poison-type Pokémon are highly toxic, and people avoid them like the plague! His starting Pokémon is a Shiny Koffing. This world doesn't yet have a Poison-type Elite Four member. Perhaps I can fill that void? Let the people of this world experience the torturous tactics of Poison-type Pokémon! Years later, Ye Kai, having become a Poison-type Elite Four member, goes even further, becoming the World League Champion. His acceptance speech is… Fire and poison are inseparable; if you play with fire, you must play with poison!