Well, I spent about 4 hours to make this shit.
dat*.pak file had the sprites and SE files.
Since this is a "please insert the disk to play" game, there's a "hidden" layer with the OST. So the game load them while you're playing, just like a lot of PS1 games.
Anyway, I used Susie with some plugins to get all sprites, GARbro to extract the *.p16 SE files in a executable format and CDmage to rip the OST.
Good luck.
https://_anon_files_com/H3D2Y769z3/toheart_dump_rar 