Prince Siddhartha is heir to the Shakya kingdom, which is constantly at war with the more powerful Kosala kingdom. His father tries to raise as him as a warrior leader and to shield him from the miseries of the world. Meeting the young outcast girl Migaila, Siddhartha experiences love for the first time but also witnesses the suffering that afflicts humankind. Meanwhile, in Kosala, Chapra rises through the military, despite his lowly origins, to become a hero and general of the army. A final showdown between the two kingdoms forces Siddhartha to re-evaluate the path he is following.

Buddha: The Great Departure

Under the impression that they saved the World of Den-O, Tsukasa Kadoya (Kamen Rider Decade) and company begin their journey to the World of Kabuto when they are halted by Sieg who presents them a manuscript that detailed the legendary Oni Conquest with Momotaros' image on it. As this occurred, the Tarōs mysteriously vanish from the DenLiner as they are about to help Kotaro Nogami (Kamen Rider New Den‑O) out with the true threat to their world.