[while it definitely wasn't English or Japanese, Prompto's native tongue should have a weird feeling of familiarity to it: almost Latin sounding with certain things that sound almost English or almost Japanese, but not quite.

oh, but then the sound comes back and he understands exactly what Ren was saying. that's kind of cool, and amazing, in a weird way. his eyebrows raise, and he takes note of what just happened.]

Shoot. Now I won't be able to understand you if you sleep talk.

[he smiles, and then notes-]

You can probably sign some basic things if you're really stuck, though! Not sure if I'll understand that either, but, never know.