Matsuo has dark brown hair and deep brown eyes, which contrast starkly with his pale skin tone. He is of a defined build, as well as a height of 5"9. His usual attire consists of a black hooded undershirt, black pants tucked into metallic braces, and traditional Japanese sandals with socks tucked in. Over his black pants and undershirt, he wears a green garb, with large holes in the sides for ventilation.
He has a different outfit prepared especially for battle, which he has dubbed the «Cyber Ronin», which was accompanied by the «Eliminator». It's composed of black leather and metal mostly. Metal covers most of the joints, as well as limbs, along with the chest, legs, and face. The armor is known for it's high defense, and ability to defend against most weapons with the metal plating.
Matsuo, out of guilt of what he did for his brother, begins to treat people respectfully, and has changed somewhat since the incident with his brother. He once used to be very rowdy, and acted spoiled and disrespectful, but became mild-mannered, level-headed, and independent. Whenever he entered SAO, he soloed for quite a while, until he realized that there was no way that he could survive on his own as a solo the entire time, and he should party up with some friends.
But the main problem was, he didn't have any friends. After Haruo was out living on his own, his social skills and many of his other skills became poor, as Haruo often guided him through most things, but he wouldn't feel right asking for help after his act of treachery, and knew that Haruo wouldn't forgive him easily. Of course, he withdrew from social skills, and followed the path of a social introvert. On SAO, he attempts to make friends, but ends up never seeing them again, although he slightly progresses. Of course, some of his interactions seem foreign, but by Floor 10, he manages to act normal.
On January 1, 2009, Matsuo was the second child of the Tsubasa family. Strangely enough, his brother, Haruo, who was born two years before him, was born on the same day, but a different year of course, and was the first addition to the family. Matsuo had a good upbringing, that was, with the exception of his parents' absence, and his almost daily arguments with his brother, although the arguments died down some by the time he turned 11, and Haruo 13, but they still occurred from time to time. In place of his parents, who were world-renown businesspeople, the void had been filled by a lax babysitter, who gave the boys almost limitless freedom, in exchange for the fact that they would never tattle to their parents.
The sitter had supervised the boys until Haruo was about 15, and Matsuo 13. Their parents had been gone for over a week, due to an international business meeting with a video game company that operated in America. Around that time, Hatsuo and Maruo had been involved in many different sports and athletic activities, which worked greatly to their advantage against the crisis that would soon occur.
Their sitter, a 28-year-old woman, arrived at their house armed with a switchblade and intoxicated. She had continued to carry on the charade of the lazy sitter, until she started acting odd, and suddenly pulled out a switchblade while Haruo and Matsuo were exercising in their makeshift gym at home. She grunted with each step, as she arrived closer and closer to Haruo and Matsuo, and slid open the door with a wicked grin and a sadistic cackle. She held the weapon behind her back and greeted them, only to stab at Matsuo's elbow. Haruo had seen the knife, and reached for a 15-pound dumbbell, and tossed it at the sitter's foot, crippling her from movement. Matsuo had been screaming from uncontrollable pain, and while Haruo reached for another dumbbell, the sitter lurched towards Matsuo, and made a final attempt to stab him, but was unable to complete it before Haruo dropped a 30-pound dumbbell onto her head, crushed her skull, and knocking her dead. Both Haruo and Matsuo were terrified at what had happened.
They checked her pulse to double-check, and Haruo, being the older sibling knew what to do, in contrast to the terrified Matsuo. While he knew it would weigh on his conscience, he cleaned up the blood and any marks of the sitter's death, and burnt her in the backyard, and as it was a private estate, he didn't have to worry. In the end, the two brothers had composed a logical explanation as to what had happened. While Haruo thought they had a mutual agreement to stick to the script and never tell anyone, Matsuo had other plans. Haruo created the story that the sitter had been run over by a car, and they accompanied her to the hospital, and when the report arrived at the hospital, her parents had been contacted, and decided that they wanted to cremate their daughter, and keep the ashes. Of course, Haruo had taken care of the ashes as well. He flushed them down the toilet, and erased any evidence, including the blade, which he hid in the attic.
When their parents arrived from their business trip, Haruo began to tell them what had happened using the explanation he had created, but Matsuo told them otherwise. Their parents were furious, and decided to keep quiet, but kicked Maruo out of the house, saying they couldn't be harboring a criminal. Haruo's body had been struck with fear, and their parents arranged for him to live in an apartment alone for the next few years, and supplied him with a more than adequate amount of money, and paid for the flat. This created a huge rift between the brothers, and until 2022, they would not cross paths. And when they finally did, the results were unpleasant, due to how strained their relationship had become that day.
Although, a major difference between them was how they had spent those 2 years. Haruo, didn't do many significant things, and went onward with his life, but Matsuo on the other hand, was tired of always being weak, and after he healed from the wound the sitter had inflicted upon him, he began practicing Martial Arts, and hit the gym every day, before and after school. Eventually, he felt safe, and as if he could defend himself, but that sense of security disappeared the moment he realized what SAO really was.
For the majority of the first 10 floors, Matsuo didn't do much but grind, and also attempted to make friends, but still, entered Floor 10 without a single friend on his friend list. Although, Floor 10 is when things start looking up for him.
Reaver - (1-hit strike) A basic sword skill that performs a downward slash.
Fell Crescent - (1-hit strike) A high-class charge-type sword skill that delivers a downward blow and covers a distance of 4 meters in 0.4 seconds.
Butcher - (2-hit combo) A medium-level attack. The user slashes down vertically with both strikes able to induce a bleed effect for 10 seconds each.
Heavy Thunder - (3-hit combo) Charging up the skill for3 seconds, the user rushes forwards to swing diagonally left, then right then straight down. The last move is powerful and used to break the block of the foe if they do not have a shield.
Horizon's Edge - (4-hit combo) A highly powerful skill. It starts with a rushing swing at the enemy's side. The user then spins to slash twice more before pivoting to the other side and finishing off the attack. The last move will induce a powerful bleed effect for 20 seconds. It will also "Daze" the foe for 5 seconds even if it is parried.