Yamato's blank demeanour gives way for a second or two when he sees the wound, and there's a few seconds where he just looks guilty and ashamed. He quickly turns away to busy himself with opening the surgical kit, angling himself so that Barry can't see his face.

"Sit down, Gramps," he says, tone still completely flat.

When he turns back around, bringing the surgical kit to rest next to him and pulling out the equipment he needs, he's back to being completely detached.