@ixsaz Her power comes from absorbing Grandpa's water. And she aged because she came back to Earth outside of Souboutei. It's only in the other planet, and in the mansion, that the passage of time is warped.
Yeah, so the real twist was that Makoto was a sister, not just possessing the body of a girl lol. The more plot-relevant reveal was pretty obvious a while ago though, more-or-less confirmed two chapters or so ago?