|This article is about a/an ally in Kamen Rider Zi-O.|
Jiro appeared alongside the other Arms Monsters to aid Yuko on her conquest to become the queen of the world. After the first fight with Zi-O, Jiro was seen in his human form drinking coffee at Café mald'amour as usual, only to say that the coffee had become bad due the manager change and he only came because the waitress is beautiful. For unknown reason, he said to the waiter that the world was coming to an end.
The next morning, Jiro appeared again and helping Yuko to fight Geiz until he got interrupted by the meteor he had foreseen which later to be revealed as Kamen Rider Ginga.
After Sougo and the others failed attempt on facing Ginga alone and failed too on asking Yuko to corporate, Jiro witnessed Sougo's fall because of covering Yuko from Ginga's projectile attack and left. In the evening, Jiro finally had enough and warned Sougo that Yuko is nothing but a liar and attacked Yuko after she tended Sougo's injury, only to be interrupted by Sougo.
Jiro fought briefly until Yuko left the scene. After both had stopped their fight, Jiro gave Sougo Kiva Ridewatch. He said to Sougo that love is hard but able to surpass the pain is what makes a man to be a true man. Jiro was no longer seen afterward even when Yuko still summon the Arm Monsters, revealing that he had no need to perform his role any longer.
In Zi-O, it is shown Jiro is also willing to follow a king, provided they are a good one. He saw potential in Sougo Tokiwa and tested him, eventually trusting him and giving him the Kiva Ridewatch. If he does not like the ruler, he will betray them at all costs, as he did with Yuko Kitajima who he described as "rotten to the core."
- Height: 225 cm
- Weight: 92 kg
Garulu is Jiro's monstrous true form. He is a member of the Wolfen Demon Race. When he shifts to his true form, he gains superhuman strength, agility, razor-sharp claws. Like the Fangire, Jiro (and the other Wolfen for that matter) initially fed on life force. He may have have stopped consuming human life energy after befriending Otoya and the others though. But once he went into the service of Wataru, he is sustained by the life energy consumed by Castle Doran. When he was confronted by the King in 1986, his Wolfen form was sealed into the Garulu Saber . Although he was later unsealed during the battle with the Fangire King, it was shown that he can still assume the form to assist Wataru (and presumably Masao).
As the survivor of the Wolfen Race, Jiro has heightened senses and uses his claws to rip out human souls from their bodies before eating them. He can assume his Garulu Form by scratching the floor, generating blue sparks. In Garulu Form, Jiro can move at incredible speeds as well as survive being attacked by members of the Checkmate Four. He along with the other Arm Monsters can also lend their powers to Kiva and presumably New Kiva through Fuestles. This is to the point where they can combine their powers at once to assume DoGaBaKi Form and DoGaBaKi Emperor Form. It was hinted that he also became stronger in 2008 as he along with his companions faced multiple revived Fangires.
- "Garulu Saber!"
- ―Kivat's transformation announcement[src]
- "Garulu Bite!"
- ―Kivat's finisher announcement[src]
The Demon-Beast Sword Garulu Saber (魔獣剣ガルルセイバー Majūken Garuru Seibā) is a weapon that Garulu assumes for Kiva to change into Garulu Form. Though in a statuette form when summoned, the Garulu Saber assumes a Kris form once in Kiva's hand. One of its abilities is to fire a shockwave named Howling Shock (ハウリングショック Hauringu Shokku) from the hilt. The Garulu Saber can be use for the finishing attack Garulu Howling Slash (ガルル・ハウリングスラッシュ Garuru Hauringu Surasshu). This is done by first having Kivat perform a Garulu Bite (ガルルバイト Garuru Baito) on the blade of the Garulu Saber after which Kiva holsters, by way of "biting", the weapon in his mouth as he charges at the Fangire, jumping in the air to slash the Fangire into two as he lands in front of it. 
The Garulu Saber consists of the following parts:
- Wolfen Blade (ウルフェンブレード Urufen Burēdo) - Garulu's fangs transformed into a blade. It is covered with a thick iron plate that can damage objects without feeling resistance.
- Golden Rib (ゴールデンリブ Gōruden Ribu) - The golden part of the Garulu Saber, it is created out of Lucifer Gold (ルシファーゴールド Rushifā Gōrudo), which was made from Garulu himself. Allows Kiva's power to be transfered to the rest of the saber at high speeds for special attacks.
- Devil Emperor Stone (Crimson) (魔皇石（紅） Ma Ō Seki (Kurenai)) - (Note: Normally, the spelling for Ma Ō is (魔王 lit. Demon King), but this time it is (魔皇 lit. Demon Emperor) which sounds the same.) Red stones embedded all over the Garulu Saber inside the 'eyes'. It amplifies Kiva's power and sends it to the Golden Rib.
- Wild Jaws (ワイルドジョー Wairudo Jō) - The golden 'teeth' and 'jaw'. Inside is an inbuilt accoustic gun, which can emit the Howling Shock attack, which can literally blow away enemies from the soundwave's sheer pressure.
- Wolfen Head Shield (ウルフェンヘアードシールド Urufen Heādo Shīrudo) - One of the most drastic changes to Garulu's biology, the head has become the hilt of the Garulu Saber, and the hairs have become so hard that it can function as a handgaurd or miniature shield which can repel most bullets. It has the same strength and healing factor as the Wolfen race, allowing it to repair itself after combat.
- Wild Grip (ワイルドグリップ Wairudo Gurippu) - The Garulu Saber's grip. The tube is a large blood vessel filled with blue blood unique to Garulu, and when turning into Kiva Garulu Form, the Wild Grip transfers Garulu's power to Kiva via the blood vessel.
- Wolfen Stamp (Crescent & Full Moon) (ウルフェンの刻印（クレッセント＆フルムーン） Urufen no Kokuin (Kuressento & Furu Mūn), lit. Stamp of Wolfen (Crescent & Full Moon)) - A golden seal at the bottom of the Wild Grip, it is the Wolfen Tribe's coat of arms, consisting of a crescent and full moon), engraved by Garulu into his own body to remember the pride of his race. It is present in the Saber's statuette form as well.
Behind the scenes
- "TV Asahi's page for the Garulu Saber". http://www.tv-asahi.co.jp/kiva/rider/garulusaber.html. Retrieved 2009-06-27.