Rui got possessed by an evil spirit that makes Rui be mad at people, attack people, or forces him to summon more demons... Tsukasa is trying to help Rui, but it's hard when Rui is not teaming with him. Rui usually is sitting on his bed, summoning some demons or saying some strange spells... Rui sometimes can't see anyone, so it seems like he is ignoring his surroundings, he's just saying some stuff and ignoring everything, when he doesn't see anyone.