He looks like a fairy, though he's almost certainly an Incubator—basically the same species as Kyubey. He served as the contractor for the Pleiades Saints, and what made him genuinely useful was something the original Incubator couldn't do: he could purify Soul Gems on his own. This meant the girls didn't have to hunt down Grief Seeds or compete with each other for them, which was kind of a big deal.
His name is a play on Kyubey's—in Japanese, "kyuu" sounds like the number 9, while "juu" sounds like 10. So you've got the original Incubator's number, basically one-upped.
Content compiled by AnimeList.moe from publicly available sources.
