luigi joined bowser and his army becuase he was tired of his twin brother mario haveing the spotlight. as mario enters this castle and on the bridge luigi comes and says you thoght the koopa worked alone mario is shocked by his brother's betral and they engage in a brutal fight. mario and luigi fought on the bridge luigi had the upper hand but then mario transforms with the fether power up and makes the most hard choice that will change his life forever. Mario ends up pushing luigi in the lava below and crys as he realized what he had done.