Okay, I can accept the bizarre notion that Mana is both MP and HP in this world, but in that case why doesn't Redia have any? Shouldn't that make her a corpse?
And if Health and Mana are separate things, then why is killing monsters based on reducing their Mana rather than their Health? Or is this somehow linked to monsters being generated from mana in the first place?
It is all very odd.
As is this obviously-a-girl character with an obviously-male name.