Isshin Ashina

Ashina Isshin was a legendary swordsman, attaining the title of sword saint and the founder of the Ashina Clan. He is a Genichiro Ashina's grandfather. When young, Isshin fought desperately time and time again, polishing his technique in the blood of his enemies. When young, Isshin fought desperately time and time again, polishing his technique in the blood of his enemies. He consolidated his learnings under the "Ashina Style" name for the sake of his clan's dominance. For his deeds, he was named the Hero of the Northern Country.

(Source: Sekiro: Shadows Die Twice Wiki)