I've only played the Japanese version, so I don't know much about levels and shit...
Did you beat the one with the ladder match against Mitsu/Voldo/Taki/Nightmare/Cervantes where you've only got 20 seconds at the start to beat each one and they're, like, super-armored? (The one inside the church)
I think that's how I unlocked subchapter 2, but I can't remember.