ISF

This is a Ikura GDL format.

This format may be complicated to reverse. The data is protected via unknown method that may use a different key with each game. After data is decrypted, the original data may be compiled from it's original form (for example, you can't just open it up in a text editor and read it). Currently unknown what character encoding the game understands.

2024

Years later, thinking about this and besides the final obfuscation to protect the script from prying eyes, more than likely compiled into byte code.