Louise Françoise Le Blanc de La Vallière is a self-absorbed mage in a world of wands, cloaks, and royalty. Although she studies at Tristain Academy, a prestigious school for magicians, she has a major problem: Louise is unable to cast magic properly, earning her the nickname of Louise the Zero from her classmates. When the first year students are required to perform a summoning ritual, Louise's summoning results in a catastrophic explosion! Everyone deems this to be yet another failure, but when the smoke clears, a boy named Saito Hiraga appears. Now Louise's familiar, Saito is treated as a slave, forced to clean her clothes and eat off the ground. But when an unfamiliar brand is found etched on Saito's hand from the summoning ritual, it is believed to be the mark of a powerful familiar named Gandalfr. Wild, adventurous, and explosive, Zero no Tsukaima follows Saito as he comes to terms with his new life and as Louise proves that there is more to her than her nickname suggests.

In the 21st century planet Earth was rendered inhospitable to life, and people mass-migrated to Planet Zi, the natural home of metallic life forms known as Zoids. Many years later, Zi faces its end. Its inhabitants partake the journey to migrate back to Earth. Attempting to regenerate the Earth to make it hospitable, the migrants come up with a Zi-Forming scheme. However, the plan fails and Earth is left in its state of turmoil. Overrun by Zoids and blanked by unstable weather phenomena, the migrants are faced with a difficult life. The Empire and Republic settlements attempt to uncover Zoids buried within the Earth to bolster their respective armies. The story picks up following second-generation Earth citizens: Leo Conrad and Buzz Cunningham, who have a chance encounter with a girl Sally Land as she flees the clutches of the Empire. (Source: Zoids Wiki)

The story centers on the Platonic Heart, a jewel that—according to an old urban legend—can grant any wish when collected. Only a chosen few are allowed to compete in the Platonic Heart hunt, and high school junior Aya Iseshima is one of 11 girls and women who are taking part.

In a remote desert on the Planet Zi, a boy named Van discovers an abandoned, dilapidated facility. Inside, he finds an opaque cocoon that breaks on its own, and a dinosaur-like robot known as an Organoid emerges from the shell. Van names the creature Zeke and claims it for himself, but a group of bandits come after him to seize the Organoid. The bandits are equipped with Zoids, beast-like mechanical units that are used for combat. Van is able to fend off his pursuers by reviving and fusing with an old Zoid dubbed the Shield Liger. Van returns to the facility with Zeke in tow and finds a new cocoon. He is ecstatic that he may have obtained another Organoid, but when the cocoon breaks, a girl emerges from it instead. Unaware of her origins, the girl only remembers that her name is Fiona and that she has to locate an object called the Zoid Eve. Determined to solve the mystery behind her existence, Fiona ventures out alongside Van and Zeke to uncover what the Zoid Eve truly is. The trio runs across many friends and foes in their adventure, encountering various dangers and experiencing slices of light-heartedness as they travel.