Kamen Rider Zein 3D model

Zein was an artificial intelligence of unknown origins that assessed the good intentions of humanity and was suddenly born into the network. By existing on the internet, it had kept the world under surveillance for some time, with even mega corporations like Smart Brain not exempt from it.

As Zein had a zero tolerance for malice, Gai Amatsu worried that it would come to conclude that humanity's extinction was required to eliminate malice and formed a reluctant alliance with the Ark to stop it. He would also attempt to persuade Kuroto Dan to help them as well. Unknown to Gai, Ark manipulated Gai for Kuroto to become Musou Gamer. According to Zero-Three's prediction, Zein also caused humanity's extinction in Yuto Sakurai's timeline.