Puzzle 043: The Armor Prank

ナゾ０４３　鎧で悪ふざけ
この中に飾ってあった鎧を着込んで遊んで
いた者がいる。
しかも、鎧を着ているときにつまずいて
頭の部分をへこませてしまったらしい。
犯人はこの中にいるようなのだが、
いったい誰が犯人だろう？

Google Translate
Who were playing in the armor was dressed in this headline. And guess I will pull the head and tripped while wearing armor. It seems that the culprit is in this, who exactly will be the culprit?

Notes on Puzzle
You are given a picture of full-body armor and four suspects. One of them wore the armor as a prank, but then tripped and hit his head. You have to figure who.