Words are not necessary. Anyone with eyes can see this is a master, arguably the greatest real martial artist to wield a sword on film.
Here's an excerpt from his Wiki bio to explain why this actor is better at sword than you and better than your teacher. Better than anyone in your school. Better than anyone in your sport. Show me the video to show me I'm wrong.
"...family as a whole were kabuki performers. He and his younger brother, Shintaro Katsu, followed their father in the theater. Wakayama tired of this; at the age of 13, he began to study judo, eventually achieving the rank of 4th dan black belt in the art.
"...Wakayama taught judo until Toho recruited him as a new martial arts star in their jidaigeki movies, originally using the stage name 'Jo Kenzaburo'. He prepared for these movies by practicing other disciplines, including kenpo, iaido, kendo, and bojutsu. All this helped him for roles."
Then you look at his filmography, see how many sword films he made, and it becomes instantly clear why he became so good. He had more time sparring with swords than everyone in the sport of HEMA combined over the last 30 years. And he didn't use protective gear, except for training. When he rehearsed and performed, it was nearly always naked steel, no protection.
When I look at "sword sparring" videos, all I see are amateurs no one ever heard of, who clearly don't know how to use the weapon or control the space, flailing around and calling themselves champions and masters.
Then, when I stop laughing at the astonishing arrogance of people who are afraid to face naked steel, even unsharpened, without all kinds of protective gear claiming to be teaching the "real thing", I rewatch this video so that I can learn something, and enjoy a real master showing off his craft.
Tomisaburo Wakayama, Rest In Peace.