...Houki is an -extremely- minor character who 
only shows up in the end of the FY TV 
series ...she is mainly an OAV character. Also, 
her hair is longer than Nuriko's was, if I 
recall, and her face was a bit longer as 
well...Nuriko had quite a round face. The beaty 
mark is a mistake on the artist's part, I think; 
many pictures of Nuriko are sans mark, as people 
tend to forget about it. Also, if I recall, that 
hanken was done as a cover for one of the first 
volumes, when Houki wasn't even a character...

-Misha