Mahou Shoujo Lyrical Nanoha A's

The story line follows Nanoha Takamachi, an everyday nine-year-old Japanese girl. Nanoha's regular everyday life ends when she rescues an injured ferret who reveals himself as a young shapeshifting mage named Yuuno Scrya. An archaeologist from a parallel universe, Yuuno came to Earth to collect a set of twenty-one dangerous ancient artifacts named the "Jewel Seeds" that he first discovered in his own world. Jewel Seeds give living beings who come into contact with them unnatural powers, often turning them into monsters, and Yuuno, injured while trying to collect them, must now rely on Nanoha while he convalesces in ferret form. (Source: Wikipedia)

Chapters 1-3 are the events that occurred between the end of A's and the start of StrikerS. Chapters 4-12 are side stories about the characters. Chapters 13 & 14 are the events that occurred after the end of StrikerS. Chapter 15 is a special from Megami September 2009 (also events after the end of StrikerS).

A crossover manga of Fate/Stay Night and Magical Girl Lyrical Nanoha A's.