Taiga's particle of light merged with a young boy named Hiroyuki to save him from a fall after his Guesra companion "Chibisuke" was kidnapped.

[5] While handling a Villain Guild-related case, a fully recuperated Taiga awakens and therefore allows Hiroyuki to transform in order to combat giant monsters[2][3][4] as two other Tri-Squad members, Titas and Fuma made their way to Earth and bonded with the former as a shared host.

In the middle of the series, his true agenda was revealed to corrupt Taiga into an evil Ultraman in order to fulfill his twisted vendetta against the former's father, Taro.

As the tension between humans and aliens begin to grow, Pirika's attempt to sacrifice herself in order to eliminate Woola leads to the realization that it was only cursed by its own hunger.

After rejecting his last chance at redemption, Tregear fought against Taiga Tri-Strium and seemingly obliterated by exposing himself to the Quattro Squad Blaster, seeing Taro's image in the young hero in his final moments.

The end of New Generation Heroes lead to the cold opening of Ultraman Taiga picking off where the titular team were chasing Tregear while the Tri-Squad continue the fight in their predecessors' place.

The film centers around Hiroyuki as the target of an unidentified opponent, forcing other members of the New Generation Heroes to appear one after another and together challenge the power of a great darkness.