One Sky, One Destiny (Union x Ninjago x Male Reader)

Y/n is a young man who believes in other worlds besides the 16 realms of Ninjago and that they share the same sky. One day, an event known as the Merge brought all the realms and different worlds combined with Ninjago, and the Ninja went missing as strange monsters known as Heartless appeared. Y/n was alone until he met Arin and Sora before being chosen by a legendary weapon: the Keyblade.