Saki and her son Koji don't get along well and often exchange insults. On this day, when they get into an argument, Saki tries to hurt him by calling him "unpopular" and "inexperienced," the words that teenage boys hate to hear the most. Trembling with humiliation, Koji vows to get revenge on Saki and get his pride back. His method is to overpower his real mother, Saki, with his penis.