Armed with a mini-punch, the main character, Punch Boy, goes through a maze of various gimmicks to Monster Castle, defeats four bosses and saves the captured Lady. In the maze, monsters are born from rock-like eggs (which can be rolled with a punch). The monster does not accept mini punches from other than the front, faints with the mini punch from the front, and can be defeated with another blow. Some eggs do not hatch, and monsters and punch boys often roll eggs.