|This article is about a/an episode in Kamen Rider Zi-O.|
Best Friend 2121 (ベスト・フレンド2121 Besuto Furendo Nisen-hyakunijūichi) is the twenty-fourth episode of Kamen Rider Zi-O. It features the debut of Woz Futureing Kikai, and the brief appearances of the Geiz Revive Ridewatch and Another Zi-O Watch.
In order to access the powers of Kamen Rider Kikai, Sworz uses Heure as a catalyst, forcing him to become Another Kikai! White Woz attempts to strip them of that power so he can grant it to Geiz to make him even more powerful. Meanwhile, Time Jacker Ora has a lot on her mind, as she makes her way to 9 5 DO with some suggestions. Furthermore, Rento is busy rampaging around the year 2121! Sougo decides to work together with the local children to find a way to stop him, but...
- "(Snores) (wakes up) According to this book, average high schooler Sougo Tokiwa embarks on a path which leads him to become the demonic king of time, Ohma Zi-O. Another Kikai appears before him. Neither myself, nor White Woz, nor The Time Jackers recognize this Another Rider. He’s an unknown Another Rider and it is somehow tide to Kamen Rider Kikai whom my lord meets in a dream."
- Sougo Tokiwa (常磐 ソウゴ Tokiwa Sōgo): So Okuno (奥野 壮 Okuno Sō)
- Geiz Myokoin (明光院 ゲイツ Myōkōin Geitsu): Gaku Oshida (押田 岳 Oshida Gaku)
- Tsukuyomi (ツクヨミ): Shieri Ohata (大幡 しえり Ōhata Shieri)
- Black Woz (黑ウォズ Kuro Wozu) & White Woz (白ウォズ Shiro Wozu): Keisuke Watanabe (渡邊 圭祐 Watanabe Keisuke)
- Heure (ウール Ūru): Rihito Itagaki (板垣 李光人 Itagaki Rihito)
- Ora (オーラ Ōra): Ayaka Konno (紺野 彩夏 Kon'no Ayaka)
- Swartz (スウォルツ Suworutsu): Kentaro Kanesaki (兼崎 健太郎 Kanesaki Kentarō)
- Junichiro Tokiwa (常磐 順一郎 Tokiwa Jun'ichirō): Katsuhisa Namase (生瀬 勝久 Namase Katsuhisa)
- Ziku-Driver, Ridewatch Voices: Rikiya Koyama (小山 力也 Koyama Rikiya)
- Ziku-Driver Voice: Yohei Onishi (大西 洋平 Ōnishi Yōhei)
- BeyonDriver Voice: AFRO (アフロ Afuro)
- Rento Makina (真紀那 レント Makina Rento): Jingi Irie (入江 甚儀 Irie Jingi)
- Kikai Driver Voice: Hisao Egawa (江川 央生 Egawa Hisao)
- Maruko (マルコ): Riki Ohkuma (大熊理樹 Ookuma Riki)
- Child: Shinnosuke Akitani (秋谷眞之介 Akitani Shinnosuke), Yuzuki Kondo (近藤柚妃 Kondō Yuzuki), Ryotaro Harago (原郷良太郎 Haragō Ryōtarō), Tomohiro Fukazawa (深澤智大 Fukazawa Tomohiro), Ako Yamada (山田亜湖 Yamada Ako)
- Kamen Rider Zi-O: Seiji Takaiwa (高岩 成二 Takaiwa Seiji)
- Kamen Rider Geiz: Yuya Nawata (縄田 雄哉 Nawata Yūya)
- Kamen Rider Woz: Eitoku (永德)
- Kamen Rider Kikai: Yuji Nakata (中田 裕士 Nakata Yūji)
- Another Kikai: Hajime Kanzaki (神前 元 Kanzaki Hajime)
Forms and Collectibles Used
- Watch used:
- Zi-O Ridewatch II
- Rider Armor(s) used:
- Zi-O II
- Watch used:
- Woz, Kikai
- Form(s) used:
- Futureing Kikai
- to be added
- As part of Super Hero Time, this episode aired alongside the 4 Week Continuous Special Super Sentai Strongest Battle!! episode 2, Battle2: The Secretive Armor of Mystery.
- Viewership: 2.9%
- Closing Screen Ridewatches:
- Kamen Rider: Woz
- Woz: Shinobi, Quiz, Kikai
- Count at episode end,
- Watches in Zi-O's possession: Zi-O, Fourze, OOO, OOO Tadajol Combo, Gaim, Kodama, Decade, W, Zi-O II, Phone, Bike, Kuuga
- Watches in Geiz's possession: Geiz, Cross-Z, Ghost, Drive, Faiz, Wizard, Genm, Build, Ex-Aid, Phone, Bike, Geiz Revive (Blank)
- Watches in Tsukuyomi's possession: Phone, Taka
- Watches In Woz’s possession: Woz, Shinobi, Quiz, Kikai
- Watches In Swartz's possession: Another Zi-O
- This episode marks the first time Sougo uses Zi-O II's Twice Time Break, as opposed to a King Giri Giri Slash.
- This is the last episode to have an Another Rider to exist with the right year of the original rider had born. Starting from the next episode, all the Another Riders are stated in 2019 instead.
- TV Asahi's official episode guide for ベスト・フレンド2121
- Heisei 20's official episode guide for ベスト・フレンド2121