In chapter 45 one of the immortals said that if he prayed hard enough they could grant his wishes. I assume that is somehow the reason he survived the last battle and even though it wasn't truly explained, Ryu is not an ordinary human at all. That's how I can more or less understand the ending, even though it was rushed.
Also, I kinda miss the the other couple from the first season ╥﹏╥
Lack of nose is bothering me