When Jiro was a baby, a massive oni delivered him to his foster parents, stating he would return for Jiro in 15 years. When that time arrives, Jiro must face enemy oni, dark cultists, and their minions while trying to protect his parents and girlfriend from their depredations. Ultimately, he must embark on a journey through the past, future, and other dimensions to embrace his destiny as Shuten Doji reborn.