I found it a while ago but it took me some time to look into. Thing is When Looking at his Human Anatomic Study skill the decription of it says that it helps find the weakness of "Umeru". I only know japanese a little so I didn't knew it what it was at time. I found it was a kanji 埋. It mean bury, be filled and embedded so not really helpful. By logic it should mean that it helps to find weakness of men or humans in my opinion, but I don't want to change it just because of that. So it be helpful if somebody more knowledgable do it as well as help me widen my knowledge on the matter.