- Main article: Ultraman Tregear#Personality
Much of Tregear's traits as the ultimate personification of temptation, destruction, despair, suffering, loneliness, and chaos carried over to Kirisaki, which is no surprise since he is the fallen Ultra's human form instead of unwilling host. With cruel eyes full of madness and amoral perception about light and darkness, he presented himself as an unsettling person who made little to no effort to hide his sinister nature and possessed a sick sense of humor to boot. Perceiving bonds with others as a taboo, he made cruel remarks while watching Hiroyuki and co.'s struggles (particularly in facing ordeals that'll put their bonds with others into a test) and snapped for the first time in his life as soon as Taiga achieved his newfound Tri-Strium form through rekindling his bonds with Fuma, Titas, and Hiroyuki, unable to fathom how much they proved him wrong about such thing.
After Ultraman Tregear defeated the New Generation Ultras and the Tri Squad 12 years ago, he came to Earth to find Taiga, taking on the form of Kirisaki to blend in with humanity.
Kirisaki meddles with the rest of the cast and is behind several kaiju attacks, either by compelling them to attack or outright summoning and/or creating them.
Kirisaki provoked Volk and his gang into stealing Alien Zetton Zolin's monster bomb for their own use, and got into a one-sided fight with Homare Soya. Homare was no match for Kirisaki, who swiftly defeated him after messing with him.Kirisaki hires Alien Gapiya Abel to get rid of the Tri-Squad. Upon meeting Abel, he is surprised that he knows that "Kirisaki" was a disguise, and transforms into Ultraman Tregear, which shocks Abel. When Taiga fought against Abel, Kirisaki was watching as Taiga used the Segmeger Ring, saying it was good that he didn't question the powers he was using.
After fighting Taiga Photon Earth as Ultraman Tregear, he draws a tarot card from a deck he was shuffling earlier, revealing the Fool.
Secretly, Kirisaki had been allowing Taiga to collect and use the Kaiju Rings, which slowly corrupted his soul. As the darkness floods him, Taiga becomes more reckless in battle, as seen during his battles against Gigadelos and Skull Gomora. When enough darkness had accumulated within Taiga, Tregear took the chance to corrupt him, shutting out Hiroyuki, Titas and Fuma in the process. Taiga becomes an unresponsive puppet which Tregear claims as his own partner, all just to spite Taro.
Hiroyuki sees Taiga in the darkness after he is knocked out by Kirisaki. Tregear suddenly appears and convinces Taiga to go further down the path of darkness, leading him to expel Hiroyuki from within himself. When Titas and Fuma tried to save him, Kirisaki summoned Hellberus and Night Fang from their Kaiju Rings to stop them, but Hiroyuki manages to get through and save Taiga, granting him his new form Tri-Strium. Enraged at the failure of his plan, Kirisaki transforms into Tregear to fight Taiga, but disappears after being hit by the Tri-Strium Burst. Descending into a fit of madness, he develops a hatred towards Hiroyuki and starts targeting him directly. To make him fall deeper into despair, he also goes after his friends at EGIS.Kirisaki infiltrates the EGIS base and launches a mental attack on Pirika Asahikawa. He somehow sees a meteor-like monster flying through space by reading her mind, and sets out to bring it to Earth. Tregear awakens the soul of the planet, Ether, by using the drill on Alien Ghos' ship. This caused the Earth to give off a signal that brought the monster towards it. Kirisaki revels in the destruction brought forth by Woola, where he admits to Pirika that he wanted both the light and darkness to be destroyed. Kirisaki attempts to convince Pirika that her sacrifice is fate, however, Pirika expresses her determination in saving the Earth and her friends from EGIS. Kirisaki summons Galactron MK2 as bait for Woola to emerge into the surface, who easily defeated Taiga as Tri-Strium and reverting the Ultra into Hiroyuki.
Seeing how the Earthlings cheered for Taiga, Kirisaki transforms into Tregear to interfere and fights against the Tri-Squad, obstructing them and their last window of pulling the plan off. Woola tried to help the Tri-Squad after recognizing them as allies, but easily gets shoved aside by Tregear. Tregear makes the mistake of firing a dark energy sphere at Taiga, which he redirects to Woola using the Taiga Wide Shot. Woola eats both attacks and its body is destroyed, while its core floats upwards and dissipates into a glittering light that spreads across the Earth, simultaneously redeeming and ending the once world-threatening Kaiju. Taiga attempts to convince Tregear to return to the path of light, but he finds those claims rubbish and attacks Taiga, forcing him to fight back. Taiga changes to Tri-Strium, which reminds Tregear of Taro. Taiga, Titas, Fuma and Hiroyuki put their powers together to fire the Quattro Squad Blaster. Tregear makes no attempt to defend himself and laughs maniacally as he is defeated.
Kirisaki presses the button at the top of the Tregear Eye to open it up, changing its design from Tregear's chest to his mask. He holds the device near his face and presses the button at the bottom, which causes the Tregear Eye to release a dark aura while his eyes shine a red light. Kirisaki then morphs into Ultraman Tregear and grows to giant size if he chooses to. Alternatively, he can also transform without the use of the Tregear Eye.
Powers and Weapons
- Monster Summoning: Simply by calling their name, Kirisaki is able to summon monsters through a purple vortex in the sky.
- Mental Corruption: Kirisaki is able to influence the mental state of other beings to cause them to rampage, an example being King Guesra.
- Ultra Psychokinesis: Kirisaki demonstrates the ability to manipulate objects with his mind, to an extent. He was able to pop a balloon from meters away with just a swift blow of his mouth.
- Hand Lightning: Kirisaki is able to fire a powerful electrical blast of energy from his fingers that can wound, stun or kill victims. He can also use it to disrupt the function of devices.
- Teleportation: Kirisaki can teleport through a purple mist.
- Kaiju Restoration: Kirisaki can summon a kaiju from its respective Ring.
Ultra Taiga Accessories in Possession
- Hellberus: Lost to Hiroyuki
- Galactron MK2: Fed to Woola
- Night Fang: Lost to Hiroyuki
- Gorothunder: Lost to Hiroyuki
Ultraman Taiga The Movie: New Generation Climax
- Kirisaki's shirt being white on the right side and black on the other reflects Tregear's amoral view of light and darkness. Additionally, along with its two-tone color, the bottom of the shirt has triangle-like cuts making it as if he were wearing a jester's uniform.