The Book of Darkness case is over, giving Nanoha and company some much-needed rest. But the peace ends abruptly as a pair of unknown mages descend on Earth, seeking a lost artifact and reigniting an ancient conflict. It's time to save the world again...

The future isn't what it used to be. Nanoha's rude awakening has left her unsettled; everything she knows has changed. In traveling the new landscape, she must unravel the mysteries of the past, and come to terms with her new reality.