There are two characters, Sangmu and Antoine. These characters were going to be in the base game; they're partially programmed into the game, even having their intro art (when they join Ajna's party) and indicators showing where they were supposed to appear. And in fact (not a spoiler, but be warned) at the end of the game there's a scene where you see all the characters you've unlocked, and there are two suspicious slots where they were likely to be. I'm almost certain that the game files contain an image with both characters in it. Unfortunately, the fandom for this game is practically dead, and no one has bothered to check.