主角·麻生胜是望月博士的助手，由于望月博士正在研制NEO生命体·ZO，麻生胜不幸成为了NEO生命体的实验品，望月博士将蟥虫的因子注入了麻生胜体内！之后麻生胜逃离了研究所，由于不能接受自己的身体所以一直沉睡在深山…… 一天，他突然感觉到望月博士的感应而醒了，原来博士他以改造了一只NEO生命体·杜拉斯，杜拉斯有着比ZO更强大的力量，而且拥有用自己身体的一部分来制作怪人的能力！ 另一方面，杜拉斯正准备捉拿望月博士的儿子·望月宏，皆因博士对宏的爱多于自己，从而使杜拉斯嫉妒不已。但幸运的是，ZO正好出现，并救了宏，与NEO生命体·杜拉斯的连翻激斗也由此开始！As do most of the various KAMEN (MASKED) RIDER television series, RIDER ZO concerns itself with a human being who is transformed into a cyborg hero and subsequently challenges a ruthless and powerful menace (frequently an alien organization using a series of bizarre creatures to enforce their will) which rises to threaten the Earth. The transition into a Rider is frequently the result of the evil entities' attempts at creating an unbeatable warrior, though in some of the previous projects, some riders have acted to create other Riders, and at least one individual deliberately became a Rider in order to exact revenge. In this case, the selected human is researcher Asou Masaru. Slightly unbalanced scientist Dr. Mochizuki is experimenting on the creation of a mysterious and vaguely threatening organism. Along the way, he pauses to create a human/locust cyborg. Alarmed at his new form, ZO retreats to a nearby forest and hides away. In the meantime, Dr. Mochizuki has finished his work and the organism is set loose on an unprepared world. ZO returns to defend the deranged scientist's young son and the world in a series of battles.
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