I can't for the life of me find the key to what I assume is the final boss room. Which really sucks, because I went straight to the new area right after the Devil boss without saving.
He didn't bother to put a save point in the start of the last zone, unlike the previous areas, so I got to trudge all the way back from end to beginning just so I didn't lose a bunch of power-up progress.
Side note, is there any point to the lust bar other than her making different moans during game over animations?
Edit: Found the key after wandering through the lazy block-wall labyrinth a little more.