"Im not gay" *PROCEEDS WITH A KISSING SCENE PANEL*
Ig it depends on the context, I'm honestly really used to hearing gay used as an umbrella term for any queer identities, and can be specified to gay men when talking exclusively about them. Seyeon does mean gay as in "man attracted to men", but I tend to assume a lot of people use it more as an umbrella term, the opposite of saying same-sex attraction and straight are the only ones to exist. I find umbrella terms easier when we don't know for sure (ie. Author or characters haven't said anything) what sexuality the characters are.
Dude looks like the type to say "No, you're not" if I asked him "Was I a good soul?"