I guess it's about time to reveal the truth, that Saike rewinds time when he dies, and not necessarily into that pond.
I don't know why everyone assumed that he had to die drowned to use his ability. From the start, I've been pretty sure that he just has to die.
My only question is, what would actually happen if he dies from his oracle... would he be stuck in an infinite loop, restarting and dying non-stop?