Keio Year 3, Hinomoto Edo, a stormy era later known as the Bakumatsu. A life-risking duel known as "Eternal", a battle permitted only to samurai. And among the common people, a "Standard Battle" without the stakes of life and death was beginning to spread. When two souls cross, history begins to move...

The time is Sengoku. Japan is fractured into many independent nations entangled in ceaseless war. At the center lies Ashina, a land of sacred earth and ancient mystery. Two decades after Sword Saint Isshin Ashina reclaimed the region in a brutal coup, a new threat emerges from within: The Interior Ministry. Desperate to protect his homeland, Isshin's grandson Genichiro turns to forbidden powers. The only hope lies in a kidnapped boy — the Divine Heir — and his silent protector: a loyal shinobi known only as Sekiro. This is the story of a lord and his retainer — and their quest to restore balance to a nation on the edge.

Dans une réalité parallèle où la population masculine est presque décimée, certains hommes sont choisis comme concubins de la shogun dans un pavillon interdit.