The Feast of Seven Blades

Before 600, the Ainu were the dominant force on Hokkaido, and their warriors ruled the northern reaches of Oyashima. A campaign launched in that year by the Iron Dynasty led to the eventual downfall of Ainu power, culiminating with an attack on a fortress located at what is now Tomakomai. More than 8,000 Ainu and 5,000 Iron Dynasty troops fell in combat, and both sides reputedly used demonic and monstrous troops.

After the battle, most Ainu either assimilated (to some extent) into Wajin settlements or retreated into the northern islands or the Central Range of Hokkaido.

The adventuring group known as The Seven Blades (two samurai, two kensai, two bushi, and a barbarian) from Miyako played a key role in the battle, infiltrating the Ainu fortifications and opening the gate to imperial forces. At least two of the Seven Blades later repudiated and apologized for their roles in the battle in general and the massacre that followed the battle in particular.