Fifteen years ago, Ukai Nanoha and her mother experienced a tragic plane crash. Nanoha's mother lost her life, and she was the only passenger to survive. It was a miracle that she made it through, as the Great Demon Maou had replaced her lifeless heart with one of his own, granting her a second chance at life.
Now, Maou has reappeared, demanding Nanoha to return his heart. She chooses to seek refuge in Mezon Aasu - a magical haven for beings like herself - where she currently holds onto Maou's heart. However, she must also take on the hefty responsibility of managing Earth Mansion, the very place Maou resides. Can Nanoha handle this daunting task?
