Samejima

A former senior in Ichitaka's high school, he is the main recurring villain of the manga. A sexual deviant, he tries to take advantage of Iori no less than three times throughout the manga with various schemes, but is foiled by Ichitaka every single time. After his unsuccessful first attempt he is expelled from the school, after his second attempt he becomes a drug addict on the verge of insanity, and plays a major role in the manga's final story arc. "Marionette King" is his Internet handle, and his real name is never mentioned in the manga (although in the Is Pure OVA, his real name is finally mentioned - Samejima).