Wataru was initially a shut-in who was so afraid of the outside world he wore allergy equipment believing he was "allergic to everything" and spoke using a large notepad of pre-written responses. However, he was slowly convinced to breathe in the air of the outside world and over time grew to be a proper man.
As King, Wataru is a king but powerful man, who goes out of his way to defend innocent lives. He and his two partners, Kivat and Tatsulot, help him transform into Kiva to protect people. His will is so strong he can force a monster to flee by glaring at it, untransformed no less, and fight monsters without even transforming first.
Kiva's base, incomplete form, based off a bat, jack-o-lanterns, and of course, vampires. It is not as strong as his true form, Emperor Form, as it lacks Tatsulot, but it is a good, balanced form nonetheless, and is still able to use all of the Fuestles.
Kiva Form as access to the Wake Up Fuestle, which allows him to execute a "Wake Up" attack, specifically the "Darkness Moon Break", an attack that opens the Hell's Gate on his right leg as day turns to night, allowing him to kick an opponent hard enough to imprint the Kiva emblem on impact and shatter monsters with ease with a force of 30 tons.
By having Kivat blow the Garulu Fuestle in Kiva Form, Kiva summons the Garulu Saber, transforming him into Garulu Form, based off a werewolf. This form is faster than Kiva Form, as well as slightly stronger, and wields the Garulu Saber, the sword form of Garulu, one of Kiva's servants. The Garulu Saber can be aimed at an opponent to "howl" at them, sending sonic energy beams at them to drive them back. Garulu Form's power is also influenced by the moon, at it's peak during a full moon.
By having Kivat perform a "Garulu Bite" on the Garulu Saber, Kiva can execute the Garulu Howling Slash attack, where day turns to night as he inserts the blade into his "mouth", jumps up, and down a spinning slash with the sword, strong enough to shatter a defending blade.
By having Kivat blow the Basshaa Fuestle, Kiva summons the Basshaa Magnum, transforming him into Basshaa Form, based off the Merman. This form is physically weaker than Kiva Form, but is somewhat faster, but has very precise and fast aim with the Basshaa Magnum. He is able to aim very accurately, striking weak points, blasting them with very powerful water balls from the Basshaa Magnum.
By having Kivat bite the hammer of the Basshaa Magnum, announcing "Basshaa Bite", Kiva can execute the Bassbaa Aqua Tornado, where he stands with the Magnum in the air, it's fins spinning as it gathers a cyclone of water around him, as day turns to night. He then takes aim and fires a very powerful ball of water at the opponent, which tracks and follows them to the end of the Earth.
With Kivat blowing on the Dogga Fuestle, Kiva summons the Dogga Hammer and enters Dogga Form, based off of Frankenstein's monster. This form is very strong, but very slow, wielding the Dogga Hammer. Despite the massive hammer and large boost to punches, kicks in this form are only half of that in Kiva Form. Kiva often drags the Dogga Hammer across the ground for dramatic effect in this form.
By having Kivat perform a "Dogga Bite" on the handle of the hammer, Kiva performs the Dogga Thunder Slap, where he opens the "fist" of the hammer to reveal an eye as day turns to night. The gaze of the eye crystallizes the opponent, as Kiva swings the hammer around, generating an energy fist above it. He brings the hammer down, swinging the energy fist onto the opponent, shattering them.
By having Kivat blow all three Arms Monster Fuestles in rapid succession, Kiva uses the power of all three Arms Monsters to enter DoGaBaKi Form. This form combines all positive attributes from his previous forms, and allows him to wield all three of the Arms Monsters weapons. As a downside, this form is very taxing on Kiva's energy, to the point that he could only use it for five minutes until it would kill him. He only used this form a few times, yet as he grew in power, the drawback became non-existent. Nonetheless, he rarely uses this form, as Emperor Form outclasses it.
Kiva can use an enhanced Darkness Moon Break in this form, using the Wake Up fuestle.
By summoning Tatsulot with the Tatsulot fuestle, or by transforming with him to begin with, and with Tatsulot announcing "HENSHIN!", Kiva's chains on his shoulders break off, causing the shoulder guards to spread like wings and release golden bats. The bats fly back and fuse with Kiva, transforming him into his true form, Emperor Form. Kiva tends to use this form over his other forms, as it has no drawbacks to it's use.
This form is easily Kiva's strongest form, having stronger punches and kicks than DoGaBaKi Form. In this form, he has access to all the Arms Monster weapons, as well as the Zanvat Sword, his signature weapon. By sliding the Zanvat hilt to the tip of the blade, and back down, Kiva charges a crimson energy wave from the sword, fired by swinging.
By the end of his initially story, Kiva learned how to perform Dark Kiva's telekinesis, which he showed by combining it with Dark Kiva's to attack the 1987 King. Kiva can use it alone, as well, by having the Kiva Logo appear to attack a foe, crackling with Fangire power. He can control the logo to slam into foes, hold them in place, or crush them.
Emperor Form has multiple finishers:
- By pulling Tatsulot's head and landing on the bat slots, Tatsulot announces "Wake Up Fever!", allowing Kiva to execute Emperor Moon Break, a dropkick attack where energy blades sprout from his legs, slashing at the opponent as he flies into them, finishing with Kiva planting his feet onto the opponent's chest.
- By pulling Tatsulot's head and landing on the Garulu Saber slots, Tatsulot announces "Garulu Fever!", allowing Kiva to use Garulu Fever. Kiva attaches Tatsulot to the pommel of the Garulu Saber, emitting a stream of fire, acting as a second blade. Kiva then does a jumping slash with either end, destroying the opponent.
- By pulling Tatsulot's head and landing on the Basshaa Magnum slots, Tatsulot announces "Basshaa Fever!", allowing Kiva to use Basshaa Fever. Kiva attaches Tatsulot to the barrel of the Basshaa Magnum, and does a backflip, before taking aim and firing several powerful tracking water ball shots.
- By pulling Tatsulot's head and landing on the Dogga Hammer slots, Tatsulot announces "Dogga Fever!", allowing Kiva to use Dogga Fever. Kiva attaches Tatsulot to the pommel of the Dogga Hammer, emitting an orb of electricity, which Kiva then slams into with the Dogga Hammer, sending it at the opponent.
- By using the Zanvat Sword's Wake Up fuestle, Kiva can execute the Final Zanvat Slash. Kiva slides the Zanvat Pommel up to the tip of the blade, and back down, turning it red. He then slashes any number of opponents any number of times, before repeating the sliding of the pommel, extinguishing the red and destroying the opponents he hit.