Masuda was involved in the early conceptualization of Pokémon alongside Satoshi Tajiri. The idea stemmed from Tajiri's childhood hobby of collecting insects.

Masuda served as a composer and programmer for 'Pokémon Red Version' and 'Pokémon Green Version' (later released as 'Pokémon Blue' in other regions) for the Game Boy. His music became iconic and contributed significantly to the game's atmosphere.

Masuda continued his role as composer and programmer for the international releases of Pokémon. His work played a crucial part in ensuring the franchise's success in global markets.

Throughout the subsequent Pokémon games, Masuda has held various key roles including Director, Producer, Composer, Designer and Planner. His influence has shaped the core mechanics, music, and overall direction of the Pokémon series.