Nanoha and Yūno say their farewells to the TSAB and they both head home.

When Takamachi Nanoha, a 3rd grader elementary school girl, finds a wounded ferret and takes care of it she finds out she has magical powers and helps it fight a monster that attacked it.

Nanoha is ambushed by Vita for her Linker Core.

Nanoha and Fate fight the much stronger Wolkenritter.

Raising Heart and Bardiche demand a new and dangerous modification to their design.

Hayate's condition worsens, and the TSAB corner the Wolkenritter.

A masked man appears to help the Wolkenritter, whose artificial nature is revealed.

Hayate's love has given the Wolkenritter emotion, and though she says not to hurt anyone, they ignore this in order to protect her.

Fate and Nanoha again confront Signum and Vita, trying to get them to open up.

Nanoha and Fate meet Hayate, and the TSAB realize that the Book of Darkness is going to kill her.

While Chrono researches Graham, the masked man- well, two of him- complete the Book of Darkness at great cost and frame Nanoha and Fate for the crime.

Hayate is engulfed by the Book's power. Chrono confronts Graham on the past and gets a new weapon.

Fate faces her dreams up against reality, while Nanoha battles the Book of Darkness.

Wolkenritter, Nanoha, Fate, Hayate and TSAB alike team up against the final enemy.

Although the danger is averted, the threat to Hayate's life remains. In view of this, Reinforce makes a fateful choice.

On the magical world of Midchilda, Vivio Takamachi is a 10-year-old girl who lives with her adoptive parents, Nanoha Takamachi and Fate T. Harlown, and goes to school with her friends Corona Timil and Rio Wesley. To celebrate Vivio entering her fourth year of elementary school, Nanoha decides to give her her own rabbit-shaped Intelligent Device, which she decides to name "Sacred Heart" or "Chris" for short. Using her new device, Vivio transforms into her mage form, taking the adult Sankt Kaiser form she previously used during an incident several years ago, which comes as a surprise to Fate. As Vivio does some late night training with Nanoha, her Strike Arts instructor, Nove Nakajima, hears about a girl going under the name of the Sankt Kaiser Heidi E. S. Ingvalt who has been attacking various people. The next day, after Nove accompanies Vivio to visit her comatose friend, Ixpellia, she is challenged by the self-proclaimed Ingvalt.

Subaru Nakajima and Teana Lanster are taking a test to increase their rank from C to B. During the test, Nanoha, Fate, Hayate, and Rein observe their progress. Near the end of the test, Teana injures her ankle, but Subaru has a plan to complete the test in time.

Subaru and Teana are informed that they have failed their promotion exam, but are given another chance by Nanoha and Reinforce to take the exam again in a week. In the meantime, they are told about the Sixth Mobile Division, which is a special division about to be formed and led by Nanoha, Fate, and Hayate. Erio and Caro make an appearance and meet for the first time.

Hayate's dream of this new unit has finally been realized and the training begins for the new recruits. New characters are introduced which gives insight to the new villan's plot of the Lost Logia named Relic.

Subaru, Teana, Caro, and Erio are still enduring hard training with Nanoha, but soon their training will be complete. They are given new upgrades to their devices and the power-limiting feature is explained to them. Afterwards, the Sixth Mobile Division must act on their first mission.

This episode marks the first mission of the new teams, as they battle several droids to recover a Lost Logia. Subaru and the others get to test out their new and improved devices. Part of Caro's past is revealed, as well as her true ability. Someone is monitoring them from a lab, gathering data mostly on Fate and Erio, who have a connection with "Project F".

Stars and Lightning undergo further training, intended to enchance their strengths and skills. Meanwhile, Hayate requests the aid of Major Genya Nakajima's 108th Ground Forces Battalion to assist Mobile Division 6 in investigating smuggling routes. Fate and Shari discover that a Doctor Jail Scaglietti is implanting Jewel Seeds into the Type-3 gadgets.

The Sixth Mobile Division monitors, and provides security for, the Hotel Augusta, where works of art, including lost logia, are up for auction. Teams Stars and Lightning face gadget drones, and another summoner who has ties to Dr. Scaglietti.

Following an averted friendly-fire incident at the Hotel Augusta, Teana throws herself into intensive training. Subaru joins her, and they devise a dangerous strategy for their next combat exercise with Nanoha. Has Nanoha taught them well enough to avoid hurting themselves at all costs?

Teana wakes up in the infirmary many hours after being on the receiving end of Nanoha's attack. She and the other young recruits learn about Nanoha's past and how she almost died several years ago on a mission due to having overextended herself, causing Teana to understand Nanoha's training methods.