@CyanHide I'll take that dare.
Ever heard of necromancy? You probably think it's all zombies and skeletons and jazz, but depending on where you look, it's not all that. For instance in the Forgotten Realms, necromancy is the type of magic that focuses on controlling the power of death, unlife, and lifeforce, essentially the modification of all living things. While it includes raising undead, it spans to things such as instant death spells or draining your target of energy, and guess what, also healing the living. That last one's debated, but for a time healing spells were considered necromancy spells.
And in case you haven't noticed, pretty much everything Keyaru did was modifying living matter, on a grander scale, where if he had a battery with sufficient magical power - the Philosopher's Stone - he could reverse the entire world back in time. The only side effect is that he experiences everything his targets ever felt, specifically their pain and agony.
But when you're stabbed a thousand times in a row, a million times each time, what's another thousand stabs?
So there's your handwave.
@snowwolf163 I gift you with this cake. I dunno why, but I felt like I should do something for you for that one.
@ShogunHachi Yeah like, the hell happened in the anime? Why was she there? Why did she die? Why did she smile when she thought he was raping her? Why couldn't he heal her, even if she were already dead, since he reversed the whole world and everybody that died when he reversed it also came back?
I HAVE SO MANY QUESTIIIIOOOOONSSS