There is English support via the English interface. The game/application is no longer available for sale. This may make it a "collectible" for those that collect games and applications (aka. "archivists").
My thoughts exactly! A user on the game's Steam page says that all of the documentation and examples are in Japanese. So unless you know how to read Japanese, it will take some time with "Trial and error" to learn how to modify the game in order to create your own fighting game.
The game/application is no longer available for sale. This may make it a "collectible" for those that collect games and applications (aka. "archivists").
https://www.youtube.com/watch?v=fv_iaAaD4WI