Chaa supplies the weapons that the SSS uses. Despite looking much older, he is about the same age as Otonashi and the others attending the afterlife school. In the light novel, it is written that Chaa was the one who discovered how to make weapons out of "dirt"(It was actually stone). We first see him when he tries to break into the principal's office, armed with a gun, but Kanade manages to subdue him. Later on, he duels with Yurippe, and after he loses, he joins the forming SSS. Chaa also mentions that Yurippe is similar to his wife. (Source: Wikipedia, Light Novel)