Madoka×Nanoha by Kazekawa Nagi Nanoha Doujin and Puella Magi Madoka Magica Doujin — Ongoing

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Two of the most badass groups of magical girls join forces to defeat Walpurgis Night with the power of friendship! And planet-destroying lasers.

Chapter 1 released Sep 20 '11
Chapter 2 released Aug 14 '12
Chapter 3 released Jun 6 '13