http://www.kirainet.com/english/hemorrhoids-%E7%97%94/
From Hector Garcia's A Geek in Japan:
"At first glance, it seems like a kid with a supercool sweater with a Japanese character. The problem is that the character η means “hemorrhoid” in Japanese. Probably the designer confused the character δΎ, which means “samurai” and is pronounced “ji”, with the character η that means “hemorrhoid” and is also pronounced “ji”… Both characters are graphically very similar but the meaning is totally different!"