魔法少女リリカルなのはStrikerS THE COMICS

This manga opens where the A's epilogue stops and runs six years forward: Nanoha Takamachi is fifteen, and the gap the television seasons leave between A's and StrikerS gets filled in. The early chapters put Nanoha, Fate Testarossa and Hayate Yagami on a Relic escort job for the Saint Church, then follow Subaru Nakajima and Teana Lanster from their first meeting through training school. Later chapters sit between StrikerS episodes and after its end, on Erio and Caro.