Seth absolutely freezes as he stares at Gyre's hands for a moment. Did he just...?
Holy fucking hell he did!
Seth immediately stops reachign for his phone and is quickly signing back very enthusiastically.

"You actually know sign language!? I haven't met anyone else who knows it in ages! Well Haizea I found out knows the alphabet but you can actually sign?!"

He seems very clearly excited about the prospect of being able to talk with someone through sign language.