Synopsis: In the past, a massive spill occurred at the Amazon experimental lab. Most of the survivors were destroyed, hot-blooded young men enjoyed hunting Amazons and the experiment seemed to be drawing to an end. Far than ending, however, it was entering a completely new phase. The number of cases of ordinary people turning into Amazons without warning was rising. The government formed a new extermination unit to assassinate people who had turned into Amazons secretly and struggled to hide the truth.
Chihiro/Kamen Rider Neo is a loner, a boy raised by Amazons who hates them but must suppress his cannibalistic urges. One day he meets Iyu, an Amazon girl who transforms into Crow Amazon and vanquishes Amazon enemies with her awesome fighting power. Chihiro is amazed at his first glance of Iyu, because she’s the first human he’s met without thinking, “I want to eat her.” She’s the first opponent he’s ever wanted to get close to, but Chihiro is unaware of her story. Iyu is a “Sigma,” a biological weapon brought back to life after her parents turned Amazon and killed her.