Kamen Rider Wiki
Kamen Rider Wiki
Icon-build.png This article is about a/an character in Kamen Rider Build.

Yoshiko Tajimi (多治見 喜子 Tajimi Yoshiko) is the Prime Minister of Hokuto. She is able to change into the Owl Lost Smash (オウルロストスマッシュ Ōru Rosuto Sumasshu) using the Fukurou Fullbottle.

Character History

Prime Minister Himuro met with the other prime ministers for their monthly report meeting via a hologram. She gave an update on Hokuto's latest projects of child care and agriculture programs and their success to Prime Minister Himuro of Touto. She then proceeded to ridicule Prime Minister Mido's efforts in Seito as selfish and ridiculous and seemingly was amused by the fact that the Sky Wall prevented the country of Japan from reunifying. When Prime Minister Himuro tried to extend his hands to shake hers and Mido's to agree on the next meeting, both left and terminated the communication. Borderline of Justice

She later berates Prime Minister Himuro for being unable to deal with the Kamen Rider and Ryuga Banjo and letting them escape into her capital. She believes that this was done intentionally by Himuro or Mido to cause widespread panic among Hokuto's citizens and that the Kamen Rider is a secret weapon of war. Her accusations are stopped as Prime Minister Himuro's son Gentoku calls her out on her seemingly hidden intent to attack Touto by causing hostility, saying they will deal with her problem and abruptly terminates her holo-transmission. Memory Starts To Talk

After the proxy fight between Build and Grease, Tajimi attempts to back out of her agreement with Touto by ordering her army to attack Touto immediately, but is stopped by Blood Stalk. When Tajimi angrily questions what he is doing and reminds him that the course of action had been his idea, a squad of Seito's Guardians storms her residence. Stark reveals that it had been his idea to send the Hokuto army for a surprise attack so that Seito could take the whole of Hokuto with minimal resistance. Prime Minister Masakuni Mido of Seito orders Tajimi be taken into custody. As the Guardians restrain her, Seito's Kamen Rider, Kamen Rider Rogue, enters the room dragging a destroyed Hokuto Guardian. Behind her disappearance which is unknown to Sawatari, Tajimi is actually abuducted by Evolto as he experiments her by fusing with Nebula Gas. As Sawatari escapes from Utsumi who abducted him, Tajimi shows up much to his shock as she transforms into Owl Lost Smash by using Fukurou Fullbottle to battle Grease until Sento intervenes to save him. However Sawatari warned him that behind Owl Lost Smash is actually Tajimi and she would be killed if Build would defeat her before MadRogue interferes to battle Build and Grease. Tajimi's Nebula Gas is later neutralized after her Lost Smash form was defeated by Build Genius Form and she forgives Sawatari for her mistakes before Evolto suddenly appears to retrieve the Fukurou Fullbottle from Sento. Sento orders Sawatari to escort Tajimi to safety.

In the new world, she is a member of Prime Minister Himuro's new cabinet and serves as Japan's Minister of Welfare.


Due to the exposure of Nebula Gas, Yoshiko was power hungry, manipulative, and willing to endanger the lives of her subordinates to acquire the Pandora Box. After the Nebula Gas was neutralized, her true personality was revealed as she displayed great remorse for her actions and asked for Kazumi's forgiveness.

Owl Lost Smash

Owl Lost Smash

Owl Lost Smash

One transforms into the Owl Lost Smash by using the Fukurou Fullbottle and absorbing multiple Clone Smash.


  • The Owl Lost Smash has the ability to fly.
  • The Owl Lost Smash is armed with the two Forest Seeker (フォレストシーカー Foresuto Shīkā) drones on its gauntlets.

Appearances: Episode 40



Behind the Scenes


Yoshiko is portrayed by Ryoko Gi (魏 涼子 Gi Ryōko), who previously portrayed Suzuko Arima in Kamen Rider W.

Concept Art

Owl Lost Smash was designed by Tamotsu Shinohara (篠原 保 Shinohara Tamotsu).

Owl Lost Smash concept art


  • Yoshiko was the only surviving Prime Minister before the world merger.
    • She was also the one with the least relevance to Evolto, which he had impersonated and killed the other two.



Icon-build.png Kamen Rider Build
Kamen Riders
Sento Kiryu (Takumi Katsuragi) - Ryuga Banjo - Kazumi Sawatari - Gentoku Himuro - Evolto - Nariaki Utsumi - Shinobu Katsuragi
Movie-exclusive: Kengo Ino - Killbus - Keiji Uraga
Drivers/Transformation Gear
Build Driver - Transteam Gun - Nebulasteam Gun - Sclash Driver - Evol-Driver
Transformation Devices
Fullbottles - (Great) Cross-Z Dragon - Sclashjellies - Hazard Trigger - Cross-Z Magma Knuckle - Evol-Trigger - Grease Blizzard Knuckle - Killbuspider - Grease Perfect Kingdom
Drill Crusher - Hawk Gatlinger - 4Koma Ninpoutou - Kaizoku Hassyar - Fullbottle Buster - Steam Blade - Beat Closer - Twin Breaker - Muscle Glove - Solstall Wings - Giant Scratcher - Space Ride Arm - Spine Knuckle - Long Range Cleaner - Trash Converter - Gold Lio Gauntlet - Multi Deluge Gun
Pandora Box - Halfbodies - Fullbottle Holder - Build Phone
Vortex Finish - Hazard Level - Project Build - Sky Wall - Nebula Gas
nascita: Misora Isurugi - Soichi Isurugi - Sawa Takigawa - Kazumi Sawatari - Gentoku Himuro
Kamen Riders: Eiji Hino - Gentaro Kisaragi - Kouta Kazuraba - Takeru Tenkuji - Emu Hojo - Hiiro Kagami - Taiga Hanaya - Kiriya Kujo - Kuroto Dan - Parado - Sougo Tokiwa - Geiz Myokoin - Tsukuyomi
Prime Ministers: Taizan Himuro (Touto) - Yoshiko Tajimi (Hokuto) - Masakuni Mido (Seito)
Namba Heavy Industries Ltd.: Juzaburo Namba - Nariaki Utsumi - Haruhiko Wanibuchi - Guardian
Hell Bro's: Fu Washio - Rai Washio - Yoshikazu Takahashi - Norio Matsui
Aliens: Vernage
Gentoku Himuro - Evolto - Nariaki Utsumi - Takumi Katsuragi - Shingo Kuwata - Eita Kawai - Yoshikazu Takahashi - Norio Matsui
Normal Smash: Fang Smash - Needle Smash - Strong Smash - Burn Smash - Flying Smash - Mirage Smash - Square Smash - Press Smash - Ice Smash - Stretch Smash
Empowered Smash: Strong Smash Hazard - Press Smash Hazard - Stretch Smash Hazard - Flying Smash Hazard
Hard/Hazard Smash: Castle Hard/Hazard Smash - Stag Hard/Hazard Smash - Owl Hard/Hazard Smash
Clone Smash: Press Clone Smash - Stretch Clone Smash - Strong Clone Smash - Flying Clone Smash
Lost Smash: Owl Lost Smash - Stag Lost Smash - Castle Lost Smash - CD Lost Smash - Scissors Lost Smash - Zebra Lost Smash
Foundation X
Kaisers: Kaisei Mogami (World of Build, World of Ex-Aid) - Nebula Bugster
Blood Tribe
Kengo Ino - Ryoka Saiga - Mitsuomi Gobara - Evolto - Killbus - Akaba (imitation) - Aoba (imitation) - Kiba (imitation) - Remocon Bro's (imitation) - Engine Bro's (imitation)
Down Fall
Keiji Uraga - Simon Marcus (Phantom Crusher)