The first of Toho and Konami's [[ChouSeiShinSeries ChouSeiShin trilogy]], ''ChouSeiShinGransazer'' debuted in 2003.

Millions of years ago, the Earth was once a [[{{Precursors}} highly-advanced civilisation]] until the day it was attacked by an alliance of alien races called "Warp Monarch". Though humanity built [[HumongousMecha giant humanoid war machines]] called "Ultra Star Gods" to defend themselves, the civilisation was ultimately defeated by Warp Monarch's superior numbers.

Now in the modern day, the LostTechnology of that precursor race is stirring, [[SuperpowerfulGenetics awakening the dormant DNA of their descendants]] in response to a new threat. Courier Tenma Kudou discovers that he is one of the chosen, [[HenshinHero gaining the power to transform]] into one of the twelve legendary warriors known as the Gransazer.

Like their ancestors, the Gransazer are split into [[ElementalPowers four elemental Tribes]]: Fire, Wind, Earth and Water. As the leader of the reborn Fire Tribe, Tenma (as Sazer Tarious) soon finds both allies and [[TheRival enemies]] in the other three Tribes [[EnemyMine as he struggles to unite them in the face of the alien menace]] that threatens to repeat the genocide of the past. Fortunately he has help, for when three members of the same Tribe unite their powers they can summon their respective Ultra Star God and take the fight to the enemy.

[[folder:List of Characters]]
!!! '''[[color:red:The Fire Tribe]]''':

* Tenma Kudou/ Sazer-Tarious (Sagittarius): The [[HotBlood hotblooded]] [[TheHero hero]]; An archer in his eagle armor.
* Mika Shidou/ Sazer-Mithras (Aries): TheLancer and Ken's CoolBigSis; in her Flamingo-based armor, she wields [[PaperFanOfDoom metal fans of doom]].
* Ken Shidou/ Sazer-Lion (Leo): TheSmartGuy and Mika's brother; he [[DualWielding wields two]] [[CoolSword swords]] in his condor-based armor.

!!! '''[[color:purple:The Wind Tribe]]''':

* Akira Dentsuin/ Sazer-Remls (Gemini): A victim of LoveMakesYouCrazy for Karin, and a SugarAndIcePersonality; his Rhinoceros-Beetle armor comes with a {{BFG}}.
* Ryoko Amemiya/ Sazer-Velsou (Aquarius): [[TheSmartGuy The smart girl]] who first saw Karin for what she really was; she has [[LuckilyMyShieldWillProtectMe twin-bucklers]] in her butterfly-based armor.
* Jin Hakariya/ Sazer-Dail (Libra): A showoff who also believes in ThePowerOfFriendship; he has [[DualWielding two]] [[AnAxeToGrind axe-tonfas]] as his Stag Beetle-armored alter-ego.

!!! '''[[color:gold:The Earth Tribe]]'''
* Naoto Matsuzaka/ Sazer-Tawlon (Taurus): TheBigGuy, TheDeterminator and the IneffectualLoner; he has two [[ShoulderCannon shoulder-mounted]] {{BFG}} in his Bull-based armor.
* Ran Saotome/ Sazer-Visuel (Virgo): The MacGuffinGirl; she has some [[AbsurdlySharpBlade mean claws]] as the leopard-based Visuel.
* Go Kamiya/ Sazer-Tragos (Capricorn): A ByTheBookCop; he has a [[ThisIsADrill mean drill]] when he activates his goat-based armor.

!!! '''[[color:blue:The Water Tribe]]'''
* Makoto Sorimachi/ Sazer-Gorbion (Scorpio): A photographer and TeamDad (an IneffectualLoner outside the perceptions of his tribe); he uses a CoolSword upon activating his Shark-based armor.
* Ai Uozumi/ Sazer-Pisces ([[MeaningfulName take a guess]]): TheChick and youngest of all 12; her Orca-based armor is equipped with a [[TheGunslinger small gun]].
* Tappei Mikami/ Sazer-Gans (Cancer): A FriendToAllLivingThings who has a crush on Ai; his Manta Ray, not Crab, based armor is equipped with yet another CoolSword.

!!! '''[[color:black:The villains]]'''
* [[spoiler: Saeki Karin]]: A disguised alien of the Akelon race. Tries to use her disguise to put the Gransazers against eachother. When she is exposed, she goes OneWingedAngel, but is defeated.
* The Impactors: A ProudWarriorRace trio consisting of [[HenshinHero Henshin Villains]]. They consist of:
** Logia: The leader of the trio. A GunSlinger who mainly uses dirty methods to get what he wants. Also likes to use the trope 'UnexplainedRecovery' multiple times.
** Radia: The hotheaded Brute. Uses an [[AnAxeToGrind ax]] as weapon. Subtlety is NOT his preferred method.
** Lucia: Almost as equally hotheaded as Radia, but completely devoted to please her leader Logia. Wielder of a [[PrecisionGuidedBoomerang Boomerang]] [[CoolSword Blade]].


!! This show features examples of:

* AbsenteeActor: Unless needed, all 12 Gransazers don't appear in the same episode. Some are justified that they're all doing separate jobs--Jin working on his fashion line, Akira and Ai working at the hospital--but others aren't excusable.
* AnimalThemedSuperbeing: Everyone.
** Fire Tribe: Birds.
*** BigBadassBirdOfPrey: Tenma (eagle) and Ken (condor).
** Wind Tribe: Insects.
*** JapaneseBeetleBrothers: Akira (rhinoceros beetle) and Jin (stag beetle).
** Earth Tribe: Mammals.
*** ALoadOfBull: Naoto.
*** PantheraAwesome: Ran (leopard)
** Water Tribe: Aquatic animals.
*** EverythingsEvenWorseWithSharks: Subverted with Makoto, save if you're a bad guy.
* CombiningMecha, HumongousMecha and TransformingMecha: The Chou Sei Shins, who transform from mecha animal to robot, and combine together to form Daisazer.
** In a neat twist, the tribes' four transforming mecha merge with a humanoid to form a dragon-shaped robot instead of a bigger humanoid.
* DisappearedDad: Ai's father. [[spoiler: He's actually Dr. Bear/Professor Wakui.]]
* DoggedNiceGuy: Jin and Tappei.
* ElementalPowers: We have:
** PlayingWithFire: Fire Tribe
** DishingOutDirt: Earth Tribe
** MakingASplash: Water Tribe
** BlowYouAway: Wind Tribe
* EnergyAbsorption: The Bosquito's modus apparatus.
* EverybodyCallsHimBarkeep: The mysterious benefactor who kept an eye on Ai addressed imself as Mr. Bear. [[spoiler: In reality he's Professor Wakui who's also her father.]]
* FreudianTrio: Each tribe is composed of one.
* GeodesicCast
* InTheBlood: Subverted; it's revealed that the Gransazers, and possibly all humans, are [[spoiler: descendants of the Bosquito. However, it's just [[MaliciousSlander propaganda]] set up by Belzeus]].
* ItsPersonal: Ai personally wants to take down Lucia [[spoiler: after the latter nearly killed Dr. Wakui/her father and also because she gave the chip to the Guntroller.]]
* LostTechnology: The Ultra Star Gods, Cloud Dragon and gunthras.
* OneHourWorkWeek: Subverted; many times we see the Gransazers doing their jobs (Tenma being a delivery service, Jin a fashion designer, Akira and Ai both working at the hospital, etc.)
* OneSteveLimit: Averted; two successive victims of the week were named Shinji.
* {{Precursors}}: Ancient Humanity.
* ProudWarriorRaceGuy: The Impactors.
* RousingSpeech: Tenma usually gives these to the members of the Water Tribe, explaining that the Gransazers are fighting together and it's nothing about tribes.
* TheSmurfettePrinciple: An interesting play: While each tribe has exactly one female Sazer to play the trope straight, the subversion comes when they all got together. The ratio is still the same though.
* SuperpowerfulGenetics
* TakingTheBullet: Subverted. Go tries to do this agaisnt Logia [[spoiler: but Tenma pushes him out of the way. Good thing too...Go would've been '''''obliterated'''' if he wasn't pushed.]]
* TokenRomance: [[spoiler:Naoto and Ryoko.]]
* UnexplainedRecovery: Impactor Logia. He clearly committed a suicide attack and when he returned, no real explanation was given apart from that Logia wanted vengeance.
* WesternZodiac: Each Sazer is modeled after a specific sign of the Zodiac.
* WhatMeasureIsANonHuman: A VictimOfTheWeek has a ''far greater'' survival rate if he is a human than if he is an alien.
* WhatTheHellHero: Tenma asks what Go was thinking [[spoiler: when Go decides to take a bullet against Logia.]]
* WhereAreTheyNowEpilogue