Hokuto Souke no Kenshiro
The man who created Hokuto Shin Ken and set the foundation for everything Kenshiro and Hyoh would inherit. He's first mentioned way back in the original series, though most fans don't learn much about him until later.
Around 1800 years ago, he trained under Seito Gekken and picked up their signature technique—the Keiraku Hikou pressure point system. Rather than stick with one style, he merged what he learned with the original Hokuto Souke no Ken approach, creating what would become Hokuto Shin Ken as everyone knows it.
The priests had apparently decided he was destined for this, which meant making some brutal choices. He killed off the other Seito Gekken disciples to keep the art from spreading and ending up in the wrong hands. The only exceptions were his lover Yāma and her brother. This experience led him to establish the "one successor" rule for Hokuto Shin Ken—a decision that would echo through centuries and create a lot of the franchise's drama.
Content compiled by AnimeList.moe from publicly available sources.