After the Vanguard High School Koshien ends, Kouji Ibuki starts having new nightmares. Nome Tatsunagi has Suiko bring him to the mansion, where they discover he can see a Dark Tower called Sanctuary that is altering the timeline throughout history. To set things right, Kouji must first fix a mistake he is destined to make. He and Suiko travel through the parallel world called -if-, where cardfights do not exist, and team up with Magical Girls Emi Sendou and Shuka, who summon Vanguard units to help repair history. The pair can offer little help, since cardfighting is of limited use against real monsters. The series blends action, adventure and comedy with magical girl elements as the four work to restore the true history.