|400,000,000 years after an advanced human civilization was destroyed by aliens, twelve direct descendants of the civilization's warriors called "Sazers" have their powers awakened and form four tribes: Fire, Wind, Earth and Water. Each Sazer is based on a Zodiac sign represented in an animal totem or spirit representation. At first, they wage war on each other, but after learning the truth of their ancestry and their reason for awakening, the Gransazer tribes unite to protect Earth from the Warp Monarch, an alliance of various alien species, from extinguishing all life on the planet. They are the descendants of the warriors from the ancient human civilization, they later learn that the Gransazers were created to protect Earth from the Bosquito.
The Fire Tribe was formed a little bit after the Wind Tribe. Karin of the Akelon race manipulated the Wind Tribe to fight against the other Gransazer. Mika was more non-sense and not thrilled about Tenma being the leader of the Wind Tribe, nor that her little brother Ken became a warrior either. Tenma was adamant at getting the Wind Tribe on their side and also joining together the other Gransazer. For example, the Wind Tribe befriended Ran and the Earth Tribe didn't know each other and they push them together as a group. Eventually Karin was founded out and then defeated, and the Wind Tribe allied with the others. The Water Tribe and the Impactors arrived around the same time. Logia stole the guncontroller to control Guntras but eventually Tenma is able to regain control of it.
Guntras is used to unite the four Chouseishin to create DaiSazer. Logia summons DaiLogian to Earth and use it to destroy the Gransazers, taking out Tawlon, Remls, before going after Gorbion in a plan to upset Tarious.When Impactor Lucia is wounded, Radia decides to complete the mission on his own. He fought Gorbion and Pisces and enlarged into a giant. Gans arrived and the gathered Water Tribe awoke Leviathan. He refused to retreat from the fight and is killed by Leviathan. Later, Lucia use Accelerators to increase her power, turning into a giant. Lucia is outmatched by Daisazer with its pilots stopping it in time before it kills her. However, Lucia succumbs to the Accelerator's effect and dies. Alien Luka was sent to Earth by Belzeus to unknowingly unseal the Bosquito, the being the Gransazer were created to defeat. The Bosquito is able to reproduce itself and when its clones are defeated, it can absorb the energy and become stronger. After Tarious uses one of Lion's Crescents to take out the ruby on its chest, the source of its power, the Bosquito is destroyed by DaiSazer.
Then the Garbans come into the picture. ogia goes to hell again after Dailogian is damaged by Daisazer, found by Belzeus, the leader of the Garban who offers him another chance by increasing his power and reviving Logia in return for the Crystal Slab by taking Mika and Professor Horiguchi as hostages to force Tenma to hand deliver it to him alone. Logia destroys a fake crystal slab and fights Tenma. He later returning to aid them in fighting Belzeus, though he still sees Tenma as an eternal rival. At the end, and bids farewell to Tenma. After that Logia realize that he was betrayed by Belzeus, he supported the Gransazers in their final battle before arresting Belzeus to face judgement at the Warp Monarch council.