Seppun Asagako

Seppun Asagako was the nickname of an oni who infiltrated in the Imperial Winter Court of 1199.

Yojimbo
Impersonating a samurai the demon was appointed as yojimbo to Iweko Miaka, daughter of the Empress Iweko I herself. They attended Imperial Winter Court at Toshi Ranbo.

Revealed
The creature managed to bypass the magical wards of the Imperial Palace. During the courtly event known as the Devil's Chase, a traditional ending to the Winter Court, in which a procession of priests was led through the Palace by the Devil Chaser, a priest bearing ancient artifacts and performing ceremonial song and dance, the oni was revealed. The song and chant from the Chase forced the oni to reveal itself.

Rampage
A battle against the oni began in the Imperial Gardens, until it fled into the city of Toshi Ranbo. The monster could not use its shapeshifting abilities because the priest continued to produce that music and importuned the Air kami to carry it across the city, playing the Devil's Chase music from the Temple of the Seven Fortunes. The oni rampaged through the city, starting in the Senzai District, facing the samurai who fought to bring it down. It then moved on to the Kurai District, killing Moshi Durucho and defeating Bayushi Atsuto.

Destruction
Desperate to put an end to the music that was preventing it from changing shape, the oni stormed into the Ichidou District. A battle was fought in the square in front of the Temple, as well as atop it. Asako Misora was killed and the oni finally broke through the Rokugani lines and began climbing the Temple, thanks to an incursion of power from Jigoku itself that boosted the oni's already preternatural strength. Before the moster could reach the shugenja atop the Temple, Toku Saiga sacrificed himself to sever the oni's connection to the boost of power. The oni was knocked from the Temple and crashed down on Yotsu Shinzai. Shinzai, bearer of the sacred Shield of the Devil's Chase was killed, but the Shield's power finally destroyed the oni.