Id keyword the site based on what the content being offered was.

If you are offering Yaoi, use that in the keywords, if you are offering Hentai, use that in the keywords, if you are offering Anime, use that in the keywords.

It has been my experience that surfers who are in to the toon niche are typically a lot more informed about it that almost any webmaster i have spoken to about the niche, with a couple of exceptions.

Even though there are differences between the various types of art available, what i have noticed most webmasters do is call it all 'anime' or 'hentai' and, because of this, they are, in my opinion, losing out sales to those surfers who do know better than them.

Regards,

Lee