After parting ways with his girlfriend, the daring baseball pitcher Hidaka sets off on a 20-day cruise all by himself. He spends the majority of his time drinking heavily, getting into fights, and trying to seduce women. However, the ship's captain, who happens to have his young son on board, is particularly irked by Hidaka's impolite behavior towards the boy when he asks for an autograph. As a result, the captain decides that the ill-mannered athlete is not welcome on the ship.