After Musashi rescues Michiru Saruwatari from a demon, his friend Kojirou Kanemaki discovers that his father was a member of the Uesugi clan. Determined to learn more about his own past, Kojirou—alongside his Kanemaki clansmen—decides to participate in Uesugi's punitive expedition against the demon lord of Awaji Island: Yamata no Orochi, an eight-headed dragon that threatens to engulf the entire region. However, upon joining Uesugi's military alliance, Musashi faces the harsh reality of fighting against powerful demons. Humiliated by his lack of power and inability to work in groups, he has to learn how to cooperate with his newfound allies. Meanwhile, the Obsidian Eight—a group pursuing the Obsidian Goddess that dwells within Musashi's body—resumes its hunt for Musashi, and plans to thwart the ongoing island operation. As the situation grows chaotic, Musashi and his friends must foil the machinations of the various factions conspiring to seize the Obsidian Goddess.

The animation is based on the fairy tale of the same name with the local sale over 100,000 copies by Jeong Chae-bong, a writer well known for his innocent and heart-stirring tales. It is a story about two orphans, Gil-son, a five-year-old boy, and his blind sister Gam-i who are brought up by a charitable monk at a secluded temple in Mt. Seorak. Gil-son, a mischievous boy, is the guide for this hour-long travel in search of innocence. Having a pure heart, he befriends all living things and communicates with clouds, birds and flowers. One snowy day, however...

Edo-period Japan stands strong and proud, decades after its imminent doom was prophesied. The new shogun, Yoshimune Nobu Tokugawa, encounters an array of traditions that, to her modern judgment, make little sense. An epidemic exclusively rages among men, resulting in men making up only one-fifth of the population. Still, three thousand young, agile, and beautiful men serve in the Oooku—the shogun's Inner Chambers. To unearth the origins of the existing hierarchy where women head their families and govern the nation, Nobu reviews the chronicles of the odd disease. Customs and traditions have changed to accommodate for the plague; these new laws dictate the current culture and reflect the cruel story of the first female shogun, Iemitsu Tokugawa. Most notably, these customs seem to lead back to the moment a young monk, Arikoto Madenokoji, must abandon his way of life and devote his remaining days to the shogun and her Oooku.

In the ancient Shakya Kingdom, King Suddhodhana learns that his wife, Maya, has a curious dream. A white elephant with six tusks enters her body—a sign that their future child, Siddhartha Gautama, is blessed. The wise prophet Master Asita sees the child and foretells that he will become chakravartin, the ruler of the world. Meanwhile, young Chapra suffers the injustice of the rigid caste system. When Kosala army marches on Kapilavastu, Shakya's capital, Chapra plays a part in forcing them to retreat. But to escape the life of slavery and give his mother a better life, Chapra joins the Kosala army and swears to rise in the ranks. As the young Siddhartha grows, he is taught everything he needs to know to inherit the throne. However, Siddhartha has no interest in martial arts or running a kingdom. What he seeks are the truths of the world and the meaning of life itself. Although Kosala's ever-expanding power threatens Shakya, Siddhartha abandons the royal life and ventures into the world to find the enlightenment he desires.