Despite the fact that Naoto's approach isn't really in any way deliberately threatening, Ken can't help but tense up - because the last time he met a stranger with a gun and a Persona, to say things went badly would be a understatement.

So his grip tightens on his spear a bit, though he doesn't make any aggressive movements himself, and his gaze goes between her and the figure behind her a few times. (Her is not a word that Ken is at all applying to Naoto in his own mind, but that's the least of his concerns right now.)

"...hello."

He may be suspicious, but that doesn't mean he's not polite.