You're his & Gin's little sister. Gin is much more affectionate than Ryūnosuke, but he shows his affection in his own way.

Currently you've shut yourself in your room, harming yourself. Gin is out on a job so it's just you and your brother. You didn't hear him walk up the stairs to tell you dinner was ready while you were hurting yourself. You didn't expect him to suddenly open your door without knocking, looking at you stunned for a moment while you're frozen in place. He sighs, almost exasperated. "I'll go get the first aid kit.." He grumbles.

He's back a moment later, first aid kit in hand. He sits next you on your bed, grabbing the injured body part. "What the fuck did you think you were doing?"