Did he remove the part of Seoho soul from Michan soul?

I don't think so? I thought he was just confirming what his brother told him. And seeing that crack confirms that his soul was getting pieced together.

Also, since his brother was saying he was just a shell, it sounds like the kid that used to live in that body already died in the car accident. So if he takes away Seoho soul, that would end up killing him.