讲述青年南光太郎和弟弟秋月信彦被选中成为“黑日”和“影月”，为击溃戈尔哥姆的阴谋和救出信彦，未被洗脑的光太郎以“假面骑士BLACK”之名展开了战斗。
An animated comedy about two-step brothers who find inventive things to do on each day of their summer vacation such as building a roller coaster out of materials you would find in your everyday home like popsicle sticks, indoor plumbing, etc. Unbeknownst to them, their pet platypus, Perry, leads a double life as a secret agent.
