Kairouseki is one of those cool AP posters even though he isn't as active as he used to be (due to working in a high paying sweatshop). Others think other things. He's still a pretty cool guy, he flirts with AP girls and doesn't afraid of anything.
He said he made the Robbybutthurt joke
Also, Kairouseki is seastone in Japanese.
According to Captain Ugly, Kairouseki represents the tarot card "The Tower".