He is best known for developing Cave Story (洞窟物語, Dōkutsu Monogatari), which has been remade many times in the years since its release.

His most popular work, Cave Story, is a freeware PC platform game released in 2004 that was created entirely by himself over the period of five years.

[6] In May 2014, Amaya released Kero Blaster, a side-scrolling platform shooter game.

[8] In 2021, Amaya was credited for assisting in the development of MIYAKOpubl's game Haru to Shura.

He is continuously developing the successor to Org Maker, the freeware audio editing suite PxTone.