While there are many ways of scoring points in the sport, the ultimate goal is to achieve "Ippon" -- a decisive move which ends a contest.
"If you win perfectly by Ippon, your opponent can be convinced that it was a perfect throw and she had lost. It is accepting your defeat. I think that's beautiful, because that's accepting yourself and your weakness."
Matsumoto admits one of her weaknesses is her diet, which she is trying to change in order to stop a long series of injuries to most parts of her body ("My arm, my nose, my fingers, and my elbow ... also my medial ligament, both my ankles.")
"Recently I've been eating a lot of organic food and stuff like that. Organic vegetables are a little expensive, but what you eat comes back around to you," she says.
"I have a really unbalanced diet, and I like sodas, coke, ice cream, snacks and chocolates and everything like that, but I'm trying to stay away as much as possible. I'm trying to control myself."
Injuries are part of life as a judoka, and Matsumoto says they provide important lessons.
"I broke my finger during the world championships, but the message then was that I was doing a judo that just pressed forward without even looking at my opponent," explains the fighter, who went from fifth in the world in 2009 to champion the following year.
"My fighting spirit was bare and raw and it lacked a cool mind, so I understood that the bare fighting spirit was not good enough. I learned through my injury that I have to have a cool mind along with my hot spirit."
However, Matsumoto's mind is clearly a curious thing -- as evidenced by her admission that she believes she once saw a fairy.
"In Japan we have tea made out of barley, and we have it in this big bucket during training which everyone can drink out of. And one time from that bucket, a tiny person this size -- like Tinker Bell without the wings -- came out and flew away.
"But that was only that time and I haven't seen any since. It just simply strayed in and then left so that it won't be found by humans."
While Matsumoto is aiming to defend her title at Rio 2016, an appearance at her home Olympics in Tokyo four years later may be a less likely dream -- but not for younger generations of judo hopefuls.
"There are many children who don't have a dream in Japan. I didn't have a dream when I was in elementary school, so I painfully understand the anxiety to that," she says.
"But by watching sports together through the Olympic Games, we can share our dreams with the children. And the more children share those dreams, the more they will be able to have their own."
While Matsumoto didn't have any particular goal -- judo was so entrenched in her life from early on that she couldn't imagine doing anything else -- there was one recurring thought in her mind.
"I used to wonder what it would be like if every single person in the world smiles at once."
Smile, and the whole world smiles with you -- even if you're a "beast."