Wataru Kurenai/Kamen Rider Kiva

Wataru Kurenai (紅 渡 Kurenai Wataru) is Kamen Rider Kiva (仮面ライダーキバ Kamen Raidā Kiba, Masked Rider Kiva). He is a shy young man who never lies, keeping to himself due to his hygiene obsession. He works at an atelier to continue his father's legacy of violin making with a dream to create the ultimate violin, using strange methods to accomplish it. But, Wataru is destined from birth to become the current Kamen Rider Kiva as his mother is Maya of the Checkmate Four, receiving a button with a diamond encrusted crown on it from her as a baby.

He teams up with Kivat to fight the Fangire race and protect humanity from them, only because the Bloody Rose orders him to "fight". But in time, Wataru learns of his family legacy and nature as a Fangire, as well as desiring to change into someone just like his father.

He later seemingly matured more by the time Decade's series started as he remained cool and calm throughout the series (although it should be noted that he still seemingly has his kind and caring side as shown in Wizard).

Evidently, Wataru is the one who inherited the mantle of Kiva from his mother, as his full-blooded predecessor was the previous King of the Checkmate Four who attempted to destroy humanity in 1986 with Otoya taking Kivat-Bat the 2nd and using it to take him down at the cost of his life. His name translates to "crimson going over" possibly a reference to his human and Fangire bloodline.