The story begins with Mario and Luigi sitting at Mario's house. Suddenly a panicked Toad running saying that Princess Peach has been captured. Mario and Luigi assume it is Bowser, like always. They go to Bowser's castle only to find that Bowser was only starting to launch his plans. Mario, Luigi, and Bowser encounter themselves with a new enemy, Count Bleck.
Count Bleck captures everyone except Mario (surprise, surprise) and takes them to a wedding where Princess Peach and Bowser are forced to marry to activate the Chaos Heart. Mario is the only one left in the room. Suddenly a pixl, Tippi, comes in and says she wants to help. At first, Mario is alarmed but tippi clarifies herself. They travel to Flipside, a dimension in between dimensions. There they meet Merlon, a descendant of the Ancient Tribe. He explains that he must travel to different dimensions to collect their Pure Hearts. He must activate the Pure Hearts in the Heart pillars scattered around Flipside. Once all 8 Pure hearts are activated, Mario can access Castle Bleck.
Count Bleck captures everyone except Mario (surprise, surprise) and takes them to a wedding where Princess Peach and Bowser are forced to marry to activate the Chaos Heart. Mario is the only one left in the room. Suddenly a pixl, Tippi, comes in and says she wants to help. At first, Mario is alarmed but tippi clarifies herself. They travel to Flipside, a dimension in between dimensions. There they meet Merlon, a descendant of the Ancient Tribe. He explains that he must travel to different dimensions to collect their Pure Hearts. He must activate the Pure Hearts in the Heart pillars scattered around Flipside. Once all 8 Pure hearts are activated, Mario can access Castle Bleck.