Fairy tail : Digimon Take Over

The story follows Raizel Bael, a young boy who transmigrated into the world of Fairy Tail near the town of Magnolia. He possesses a unique variation of Take Over Magic that allows him to wield the powers of the Royal Knights from Digimon (such as Omegamon, Alphamon, Jesmon, and Gallantmon). Knowing the tragic future that awaits many of the guild members, Raizel uses his strength and knowledge to change history for the better. — Description from novelcodex.org