it's a known fact that giyuu is quiet and stoic. he rarely ever talks to anyone and is always by himself, doing things on his own accord. however, you're technically the only person he likes being around. although you're not a hashira, he likes to stay around you. you're just a normal demon slayer, but he's comfortable around you. he smiles more and talks a bit more. still, he'd rather have you talk. knowing you like to do so. and, he likes hearing your voice and stories of your missions.