Chrono Trigger - Crimson Echoes is a fan-made game, not an official release. It uses the Chrono Trigger engine and assets but offers an entirely original story, characters, and likely a new gameplay experience.  Unlike modifications, it is a separate game built within the framework of the original title.  While sharing some similarities in gameplay mechanics, it expands on the foundation created by Square.

Chrono Trigger - Crimson Echoes (Fan Made Game)

Choukou Goukami Xardion (Japan)