|This article is about a/an transformation belt in Kamen Rider Den-O.|
The Transformation Belt Zeronos Belt (変身ベルト ゼロノスベルト Henshin Beruto Zeronosu Beruto) allows Yuto Sakurai to transform into Kamen Rider Zeronos. It uses the Up Set (アプセット Apu Setto) system and the Zeronos Card (ゼロノスカード Zeronosu Kādo) to transform and switch forms.
To transform into Zeronos Altair Form, Yuto slides a switch on top of the Zeronos Belt and inserts a Zeronos Card with the green side facing forward, both the belt and card forming the letter A. For Vega Form, Deneb stands behind Yuto while in Altair Form, whom repeats the process, but instead inserts the Zeronos Card with the yellow side facing forward, both the belt and card forming the letter V. After using the Red Zeronos card, Yuto inserted the card with the red side facing forward, making the belt going into its Altair mode while the "Z" is on the red side of the Zeronos Card, activating Zero Form.
There are several kinds of Zeronos Cards: The original cards had a green side (for Altair Form) and a yellow side (for Vega Form). A special variant of the Zeronos card had the original green side, but a red side in place of the yellow side in order to start the process of changing Altair Form into Zero Form. All subsequent cards thereafter replaced the Altair Form side with the Zero Form side, but retained the Vega Form side.
A Zeronos Card can only be used once; when Zeronos cancels the transformation, the card evaporates if it is the yellow or green Zeronos Card, but rusts and breaks if it is a red Zeronos Card. In his debut, Yuto possessed ten green sided Zeronos Cards in a card holder on the Zeronos Belt until he used up the last in Episode 32. These cards are based on Yuto, representing the memories of those who know him. When a card is used, the memory of the elder Yuto's existence in the present time is erased from the memories of people who are not Singularity Points. In Episode 35, the elder Sakurai offered Yuto a new full cardholder and one extra Zeronos Card. After some hesitation, Yuto accepted the offer and used the extra, displacing the elder Sakurai from the time they were in.
It is to be assumed that the new holder has infinite cards left as long as there are people to remember him. When Yuto used the red sided Zeronos Card, it used the memories of Airi as a catalyst to permanently change Altair Form into Zero Form. All subsequent red Zeronos cards now use the memories pertaining to Yuto instead of his future self. Although Yuto eventually uses up all of these new cards, in the finale, Deneb presents him with the last of the original green Zeronos cards. Through unknown means, Yuto eventually reappears with a new set of green Zeronos cards, allowing him to join Den-O in the fight against Negataros, most likely meaning that Sakurai is on the verge of returning to history. 
- It is unknown what would happen should Yuto use the yellow side of a Red Zeronos card while in Zero Form, compounded by the fact Deneb is transformed into the Denebick Buster and unable to assist in the transformation of Vega Form.
- "TV Asahi's page on the Zeronos Belt". http://www.tv-asahi.co.jp/den-o/rider/belt_zero.html. Retrieved 2010-08-03.
- "TV Asahi's page on the Zeronos Belt with Red Zeronos Card". http://www.tv-asahi.co.jp/den-o/rider/belt_zero2.html. Retrieved 2010-08-03.