Historical figure. Buddhist monk turned outlaw and retainer for Minamoto no Yoshitsune.
Famously tried to take the weapons of 1000 unworthy swordsmen, but supposedly stopped short at 999; Yoshitsune was the last person he faced and lost twice to before becoming a retainer. His death- a standing death after getting riddled with arrows and fighting off some 300 soldiers- is also an iconic piece of history concerning him.