Dune

A demon who roams the desert Dune has ochre eyes light orange/brown ivy green hair and tan skin whereas everyone else is pale. He absorbs negative energy from people leaving them with only good feelings shown by two male rivals who get very intimate when he absorbs their negative energy and uses the energy to become more powerful. This increases his height and apparent age. Fully charged he takes the appearance of a tall muscular young man. If he has little energy he takes the appearance of a somewhat scrawny teenage boy. He seems to have a soft spot for Shizuka. He came into the story by taking negative energy from Tonaes school. After being discovered and promptly defeated by the protagonists Shizuka the schools president offers Dune the opportunity to become a student and help stop fights. He accepted this offer and is currently attending the school