Sekiro Kuroki

Sekiro grew up as Rakuyou's closest friend in the Oni clan.

When Rakuyou was appointed as chief, Sekiro became his right hand and advisor. For a long time they held a diplomatic friendship between the spirit world and the human world. When Rakuyou fell in love with a human woman, everything changed.

The head of the clan cultivated a closer friendship with the humans than with his own tribe And wenn the humans asked him for help in defending the city, he did not hesitate and sent his fighters to the human world. To the reluctance of his own people. They followed the call of their chief and stood by the people, including Sekiro. Sekiro's older brother, Roca, stayed with the clan. He was not a great fighter and preferred to take care of the clan's administration.
What neither of them knew was that it was an ambush to get the rare treasures and techniques of the spirit world. The troops of the Oni tribe were separated and the combined forces of the humans were able to enter the clan territory unhindered. The human troops had an easy time of it, as for the most part the elderly, women and children were left behind. During the raid, Roca was killed while protecting the hall with the women and children.
When Rakuyou and Sekiro arrived, Roca was already dead.
Some of the clan was saved, but the village was devastated and they suffered many deaths.
Sekiro blamed Rakuyou because he blindly trusted Humans. He left the clan and moved to the mountains, far away from what reminded him of his brother.

Sekiro swore to take revenge and avenge the death of his brother.
In an ancient ritual, he sacrificed his left eye to track down the woman who had blinded Rakuyou with love.
The gift he received was Setsuko. A young woman born Out of revenge and from his left eye. She showed no emotion and obeyed the orders of her master. She possessed the gift of detecting any being with the help of a personal object. Whether in this world or the next.

Whenever Setsuko was active, his left eye turned a deep orange and he could see with her eyes.
This is how he managed to track down and kill Elodie.. He pinned the crime on a political group that fought against the alliance between humans and spirits.

Furious, Rakuyou declared war on the Humans .
Sekiro's plan to create chaos and havoc was complete.