He Who Fuses Fate and Cheats It

At the Awakening Ceremony Henry draws ten cards and all ten come up white, the lowest grade there is, and the academy makes a joke of him. Then the Magic Card Synthesis System opens to him, which lets him fuse weak cards into stronger ones and, far enough up the chain, into figures out of myth. He starts with the cheapest white cards he can get and synthesises his way up from there. He summons the Stormfire Prince, clears monsters in the sealed realms and beats students who ranked far above him at the ceremony. The Monkey King and the Moon Maiden come into the deck later, and Henry keeps building it.