Yamatokuni is a former Yokozuna and the greatest japanese sumo wrestler. Through out his careeer he obtained 31 championships.
He is notorious for using Left Arm Clamp to set up his throws, but unlike his son, he knows when to pull back to ensure opponents are not injured in matches.
When Yamatokuni faced Jinou, he was defeated without being able to lift a finger. The next day Yamatokuni announced his retirement.
Because he never let his son wrestle since he lacked restraint, when Sosuke returned to fight at Inter-High against Tennouji Shido for semi finals of individual bouts, where the title of the second high school yokozuna is at stake, he realized that his son has honed in his serene mentality of fighting, and managed to defeat Tennoji by force out after a long and evenly-fought match.