They don't die. Ever. Not even past the heat-death of the universe. Ever. Even as everything else has ceased to exist. EVER.
NegativeSoul said:
Well, they'd be the perfect crash-test dummies. Not like they have to worry if that thing explodes into a ball of raging flames.
Except they heal before you can actually record what damage was done to them.
Also, Moukou may be immortal, but she still dislikes pain (she gives up against the heroines after they hurt her so much that Moukou just doesn't want to fight anymore), so she may not be risk-averse, but she still wouldn't WILLINGLY hurt herself grievously.