[He IS super old, he just spent most of that time being old in a place with no water-

Regardless, Vash is already crouching down next to the water's edge as Ain explains what it is, peering at his own reflection in the surface before its suddenly broken up by Ain unceremoniously getting into it. He's a bit surprised by just how fast Ain stripped, but once he explains why...Vash's expression softens, and he sinks to sit properly on the ground.]

It's okay. I don't think we were followed...and there's no way anyone could find us out here otherwise. We'll be okay for the night.

[Why can't they just live in the forest as hermits is the next obvious question.

BUT. If Ain says that the hot spring is safe, and is already IN it...it must be, right? So, after a moment of eyeing him in the water, Vash rolls his shoulders and shrugs off his jacket before stripping down the rest of the way, kicking off his shoes and setting them next to where he laid the rest of his clothes. He pauses just long enough to pull off his arm before joining Ain in the water, and.

Oh. Oh. Oh, it's so warm...]