Is this it?
The Truth of the Ancient Ways: A Critical Biography of the Swordsman Yamaoka Tesshu
https://terebess.hu/zen/mesterek/anc.pdf
Tessu was not only a samurai warrior but also a bodhisattva warrior.His life exemplifies the highest tradition and teachings of Samurai warriorship and service.If I had one word to describe him, I would say it is “Reiho Chusetsu,” unshakable egoless devotion and loyalty, walking fearlessly through life with a completely uncovered mind/heart
( kokoro).He was so powerful with the sword that if he countered a low strike with a boken, it would actually cause his opponent to flip in a somersault.