Though they certainly are fighting to the point one could consider them to be fighting "to the death", it's quite technically impossible, unless you count the temporary deaths before their resurrections, then I guess it's more of a misnomer to call it fighting to the death when they can still keep at it after dying, when the original saying implies this will be the end for one or both of them.

Actually, it implies they'll fight each other until one of them is dead.
Sure, they can't really die, but that won't stop them from trying. Forever.

Sort of like a straight line is a curve with infinite radius.

They *can* die. But they'll get better.

HakureiSM said:

Actually, it implies they'll fight each other until one of them is dead.
Sure, they can't really die, but that won't stop them from trying. Forever.

Sort of like a straight line is a curve with infinite radius.

I can only imagine here a sine or a cosine graph.

Honestly speaking i don't think we need it. there's already tons of pools that aren't needed.
search "to the death" and Mokou and you only have 2 pages let alone with just her and kaguya specifically.

just not enough to make a pool in my opinion