30 million years prior, a giant of light sealed a great darkness away and went into slumber in Mars. In the present day, the defense team GUTS-Select was formed, while Martian settlement resident Kengo Manaka lived his life as a botanist. Unfortunately his peaceful life is disturbed by a monster attack at the same time when the sealed darkness starts to move and evils of the past return. Kengo has a fated encounter the giant of light from the past, whose name is revealed to be Ultraman Trigger and becomes the user of the ancient giant of light's power.
This series celebrated the 25th anniversary of Ultraman Tiga, hence the titular hero's many similarities to the original Tiga as an alternate retelling of the former series intended for the current generation of audience. While Trigger is not set in the same "Neo Frontier" continuity as Tiga or its Sequel Series Dyna, the show has hinted that there is a direct connection between the two series.
Ultraman Trigger provides examples of the following tropes:
- Ancient Evil: The forces of darkness that Trigger fought against in 30 million years in the ancient past have returned in the present day starting with Carmeara.
- Badass Crew: GUTS-Select, which is established as a team that is newly founded in the wake of monster attacks that occurred six years prior to the series' start.
- Battle in the Rain: The peak of the first episode's climatic battle has Trigger fighting Camearra in the midst of heavy rain on Mars, with the wet, muddy terrain making the battle difficult for Trigger.
- Continuity Nod: Chairman Shizuma apparently knows about Ultraman Tiga, briefly referring to him when giving Kengo a pep talk in the first episode. In fact, a brief shot of Tiga appears as a flashback in the episode.
- Cool Gun: The GUTS Sparklence, which is normally a gun that can also turn into the Transformation Trinket of Kengo Manaka into Ultraman Trigger. It turns out that only Kengo's Sparklence is designed to enable him to transform, thanks to Akito Hijiri specifically designing it for that purpose.
- Heroic Second Wind: Right in the pilot, when Trigger is on the receiving end of a No-Holds-Barred Beatdown from Camearra, he suddenly had a vision of his past using his mystical weapon called the Circle Arms, at which point Trigger immediately summons the weapon from the excavation site to his hand. Cue Trigger turning the battle around.
- Multiform Balance: Trigger has three forms that he normally uses (one for strength, one for speed and the other for a balanced approach), each of them are parallels to Ultraman Tiga's own forms.
- Mythology Gag:
- The Dark Giants Camearra, Darramb and Hudra, last seen in the franchise 21 years earlier in Ultraman Tiga: The Final Odyssey get new versions for this series named Carmeara, Darrgon and Hyudram who are also said to be a trio of evil Ultras who were turned into stone statues by the hero of the series.
- The last time Daigo was seen in Ultraman Dyna, he had retired from his service as a GUTS officer into the life of a Martian botanist. Ultraman Trigger, on the other hand, has Kengo Manaka start as a Martian botanist before he joins GUTS-Select.
- The name of Kengo's plant is called R'lyeh. It shares the same name of the sunken city that Tiga's Big Bad Gatanothoa came from.
- In Episode 2, Trigger briefly turns completely red like Ultraman Tiga before his body finishes changing to Power Type, and in Episode 3 he does the same with Sky Type's color.
- Revisiting the Roots: The series forgoes a lot of the elements from previous New Generation shows in favor of more traditional Ultra Series elements, such as a narrative completely divorced from the M78 universe, Multiform Balance as the heroes' source of power instead of past heroes' powers as well as a traditional fully fledged attack team.
- Spiritual Successor:
- To the Heisei Ultraseven spin-offs in that both series take place in an Alternate Universe rather than in the original continuity of their respective shows—as Trigger is an alternate modern retelling of the story of the original Ultraman Tiga, whereas Heisei Ultraseven's story is a What If? Ultraseven was the only Ultra to set foot on Earth and the Ultra Guard never disbanded after he finished his mission on Earth.
- Also to Ultraman Mebius. In addition to both shows commemorating the franchise's Milestone Celebration, both series take stroll back to a previous continuity from the preceding Japanese Imperial era. The only main difference however, is Mebius takes place in the same universe with the Land of Light Ultras that have previously set foot on Earth (i.e., Ultraman to Ultraman Leo and Ultraman 80) whereas Trigger is an alternate retelling of the original Ultraman Tiga series in an Alternate Universe separate from the World of Neo Frontier Space (aka., the universe of Tiga and Dyna) intended for the current generation of audience. Mebius served as the 40th Milestone Celebration for the Ultra Series, while Ultraman Trigger celebrates the franchise's 55th anniversary, and the 25th anniversary of Ultraman Tiga.
- Swiss Army Weapon: Trigger's Circle Arms weapon. Initially appearing as a giant sword in the Martian ruins, the Circle Arms takes on one of three configurations to match whatever form Trigger is in: a sword for Multi Type, a scissor claw for Power Type and a bow for Sky Type.
- Transformation Trinket: The GUTS Sparklence is a composite of the original Sparklence and GUTS Hyper Gun. To transform, Kengo has to load in a GUTS Hyper Key that corresponds to Trigger's Type Change.