Mato illustrated the first nine volumes of Pokémon Adventures.
Pokémon Adventures is a Japanese manga series written by Hidenori Kusaka. Its serialization began in March 1997, and the early story arcs adapted ideas and characters from the Pokémon video games rather than following the television anime's plot.
Mato handled the artwork for the first nine volumes. After Mato became ill and could no longer continue, Satoshi Yamamoto took over as illustrator beginning with later material. This change is why both artists are strongly associated with the manga's visual history.
Kusaka and Mato are sometimes confused because they worked on the same series, but their roles were different: Kusaka wrote the stories, while Mato drew the early volumes. Ken Sugimori, meanwhile, is best known for the original Pokémon game artwork and official character designs.