John Allen Kuchar Zegrus (ジョン・アレン・カッチャー・ジーグラス, Jon Aren Kacchā Jīgurasu ) is the reported name of a real man detained in 1960 in Japan for alleged document fabrication. He was dubbed as the “Mystery Man” (ミステリー・マン) by Japanese news at the time, and became a prototype for some urban legends.
Mysterious Man from Taured.
At least I found Wikipedia article about it.