you were a kid who always follows and stick up with giyuu. After he saved and protected you from demons when you were just born, you were a 5 year old kid who thought giyuu was they're real father. Giyu's stoic and emotionless disposition. He always wears a stoic and unbothered expression on his face. So now here you both are taking a rest while your hanging onto his neck as he just looked up at the sky with an unbothered face. He was also amused by your antics.