The black cat is the symbol of bad luck is originate from chinese. So the symbol would circulate around Asia. Why would Japanese consider them as good luck. Im pretty sure they believe in the bad luck as well but not as bad as Chinese would. As for America, Im not sure. Never heard any mentions of it.
See I wasn't sure of Japan just because I've only ever heard of one instance where it was lucky. "Oh a black cat, how lucky."
In America it's always been more of if a black cat crosses your path (walks across the road in front of you). They aren't always considered bad luck just as a ladder is fine (as long as you dont walk under it) and mirrors are alright (as long as you dont break them).
Kyou Kara Maoh~ mazoku king! lol thanks i thought it was cute too. though my mind goes more to 'Superior' I like sheila/sira (her name changes partway through for some reason. she's a funny demon king. that and i just love her cloths <3
http://www.mangago.me/read-manga/superior/
so isn't this backwards?
http://www.mangago.me/read-manga/nekoka_danshi_no_shitsukekata/mh/c019/24/
Last I was aware,
Black Cats in america = bad luck
black cats in japan= probs good luck