[Subaru opens his mouth to reply for Kamui-- then closes it again, unable to speak, and gestures at the vampire's eyes, instead, looking almost beseechingly at his Kamui. He can't see, we have to help him!
Subaru considers for a second, and then mimes writing something, looking around for something to write on-- oh! He finds a pen and a piece of paper and quickly scrawls down 'we should stick together'.]