When Luigi sought for courage in order to be the number one, he found a mysterious book with a strange "Courage" spell. Unfortunately, this forbidden spell bound his soul with Link, and their bodies were merged.
As Luigi and Link are forgotten by all in Hyrule and the Mushroom Kingdom because of the spell, they both agreed on searching a way to cancel this form, under the name of Rinkuji.
(Mario/Zelda crossover AU)