Yomei was the former head of the Heishi Clan. A decade ago, he was cursed by unknown means, and began to lead the clan down a dark path.
Because of this, his brother Azuma Mori (Heishi) left the clan. Yomei considered this a betrayal - and eventually took the life of his brother out of anger.
The same day, Yomei was slain by his brother's apprentice, Jin Mori, with his own sword, the Shingase.