Several months have passed since the Jewel Seed incident, and Nanoha Takamachi is getting ready to welcome Fate Testarossa back from her trial with the Administrative Bureau. Having received conditional clemency for her role in preventing the crisis, Fate has been allowed to attend school with Nanoha. However, before the two girls can settle into their daily lives together, a group of dark mages suddenly descend upon them. Overpowered by their unknown assailants, Nanoha and Fate have their mana absorbed by an ominous grimoire, and both Raising Heart and Bardiche are damaged in the process. The ones behind this ambush are known as the Wolkenritter, and its four members—Vita, Signum, Shamal, and the familiar Zafila—were summoned by the Book of Darkness to carry out its malignant bidding. The book's current owner is the young girl Hayate Yagami, oblivious to its true nature while the Wolkenritter, charging its power with the forcibly stolen mana, is duty-bound to seek the tome's completion. Left drained and weaponless, Nanoha and Fate must race against time to recover their strength and confront the Wolkenritter, with the aim of preventing the quartet from finishing the Book of Darkness and unleashing its devastating magic upon the world.

After solving the incident of the scattered Jewel Seeds, Nanoha Takamachi happily returns to her everyday life, though now with added magic practice in the morning. Exchanging video messages with Fate Testarossa and the crew of the Arthra, Nanoha eagerly awaits the chance to speak with them in person again. But while studying in her room one day, Raising Heart suddenly calls out to Nanoha and warns her of an incoming attack! The attacker is a young girl named Vita, who calls herself a Belka Knight. She proves her strength by using an intelligent device with a mysterious cartridge system to quickly overwhelm Nanoha. Luckily, the Space-Time Administration Bureau is able to step in before she is completely crushed. Vita and her fellow knights Shamal, Signum, and Zafila are on a mission to steal magical power from mages in order to complete the Book of Darkness, one of the Lost Logia. For what sinister purpose are the knights after this Book of Darkness?

Second season of Mahou Shoujo Nante Mou Ii Desu kara.

Sasami's always been kind of neat... but now she's been imbibed with a healthy dose of magic (which she plans to use to right the things wrong with the Earth, and, of course, help keep her brother Tenchi out of trouble). Naturally, there's going to be trouble: this time, it's the mysterious Pixy Misa... and Ryoko going at it against Ayeka (as usual) isn't making things any easier for her! (Source: AnimeNfo)