Folders

• aex: various sprites
• back: backgrounds
• bgm: background music
• chara: character sprites
• font: font
• script: scripts
• sse: miscellaneous sounds
• sub: no idea
• system: UI sprites. Some contain text, for example for the options screen.
• xls: some kind of text, not sure what though. If they turn out to be important for the translation I will look at it closer.

Opening the files

• Scripts: use the editor.
• Sprites: all the images are saved in TIM2 format, which can be opened with for example Rainbow.
• Background music: seems to be in RIFF WAVE format. I was unable to open it however.
• Other sounds: HCA format. I didn't try opening them yet.
• Font: no idea what to do with it.