Wataru

"He believes... in the law. Despite that, he believes! You gave up! You lost to your own weakness... and forsook the law. But Wataru... fights for those who believe. That is what a king is! The qualification of a King!"

- Tsukasa talking about Wataru to Beetle Fangire

Wataru (ワタル) is the resident Kamen Rider of the World of Kiva in Kamen Rider Decade.

Wataru
He is a twelve-year-old half-Fangire boy, having the ability to transform into Kamen Rider Kiva (仮面ライダーキバ) with the aid of Kivat-bat the 3rd. Referred to as the Prince (王子) by his servants, Wataru is reluctant to claim the title of King (キング) of the Fangires. He finds the overseeing of the ceasefire between humans and Fangires a very troublesome and unnerving task.

Biography
Wataru first meets Tsukasa and Natsumi at Kurenai Manor where he is playing his violin. Later during a misunderstanding, Wataru transforms into Kiva to fight Decade, who he believes is the devil. Yusuke arrives and clears up the misunderstanding, offering his aid to Wataru and his task of serving as King. The next day, Wataru is confronted by the Beetle Fangire who intends to become the new King. The Beetle Fangire successfully claims Kivat as his own in the ensuing battle and proceeds to absorb the Arms Monsters into his Fangire armor, allowing him to become Kiva DoGaBaKi Form. After listening to Tsukasa make a speech about his ideals for the coexistence of humans and Fangire, Wataru takes back the power of Kiva, teaming with Decade to fight the Beetle Fangire. With a combination attack of Decade's Dimension Kick and Kiva's Wake Up (Darkness Moon Break), the Riders defeat the Beetle Fangire, who is later revealed to be Wataru's father, the former King.

He later appears in the World of the Rider War as his reality is absorbed into it. Leading the Riders of his world, Wataru refuses to listen to Tsukasa and Yusuke in uniting all Riders to defeat Dai-Shocker and stop the convergence of the worlds, while in grief over IXA's death. He even went so far to allow the Queen of the Fangires, Yuki, to marry Apollo Geist for the World of Kiva to have an advantage over the other A.R. Worlds, but later changes his mind when the Fangire betrayed them to Dai-Shocker. After defeating Super Apollo Geist, the convergence of the worlds continues and the World of Kiva and Wataru disappear along with the World of Hibiki and Asumu after the destruction of Super Apollo Geist by Decade and Diend.

However, in Kamen Rider × Kamen Rider W &amp; Decade: Movie War 2010, he is resurrected after Tsukasa has been killed by Kamen Rider Kiva-la. He later appears alongside the Riders of the Nine Worlds to revive Tsukasa and help him battle Super Shocker, assuming Emperor Form with the help of Decade's K-Touch and later uses Castle Doran to fight the Super Crisis Fortress.

Later appearances
Movie War 2010 currently remains the last appearance of Wataru. The Kiva that appears in OOO, Den-O, All Riders: Let's Go Kamen Riders and Kamen Rider × Super Sentai: Super Hero Taisen is the original Kiva, Wataru Kurenai.

Forms
Just like the original Kamen Rider Kiva had various forms into which he could change into for different powers and specialties, the Kiva appearing in Decade has this same ability. The forms Wataru has transformed into are Kiva Form (キバフォーム), Garulu Form (ガルルフォーム), Basshaa Form (バッシャーフォーム), Dogga Form (ドッガフォーム). Kamen Rider Decade's Final Form Ride allows Kiva to change into the Kiva Arrow (キバアロー).