Like the opposite of a blink of shock, Potemkin opens his eyes when he feels a kiss where he can't see. The juncture of his neck is the closest there is to a vulnerable spot on this man who is built like a tank. That he can expose it utterly with only a brief murmur in reaction is a show of how comfortable he is around Ky.

He doesn't have to unbar his arms from Ky any earlier than until he asks.