Zein (ゼイン) is the main antagonist of Kamen Rider Outsiders. It is a mysterious A.I. that claims to be the embodiment of human benevolence and seeks to establish a world without malice, drawing the attention of Ark and other returning villains such as Foundation X to oppose its existence. However, Zein's methods in dealing with evil would gradually become brutal and oppressive than heroic and later on, plans to use Kamen Rider Chronicle to push humanity towards the path of self-destruction.