Jun Kazu (加頭 順, Kazu Jun) is the final antagonist of Kamen Rider W. He was a researcher of Foundation X wearing a lab coat at almost all times. He also appeared in Kamen Rider W Returns: Eternal, a prequel to the main TV series. Initially taking the form of the incomplete Kamen Rider Eternal (仮面ライダーエターナル, Kamen Raidā Etānaru), he later became the Utopia Dopant (ユートピア・ドーパント, Yūtopia Dōpanto).