Matsumoto was an antagonist in Kill Bill Volume 1.
He was a pure evil Yakuza boss in Tokyo, Japan and who was responsible for the deaths of O-Ren Ishii's unnamed parents which ultimately led to O-Ren to purse her own quest of vengeance against the Yakuza boss.
One evening and when O-Ren was nine years old, Matsumoto and his men presumably broke into the Ishii house one evening and as Matsumoto watched, two of his men fought Mr. Ishii while another held Mrs. Ishii hostage by using a sword and although Mr. Ishii put up a brave fight against Matsumoto's men, two of whom Mr. Ishii killed, one of them eventually got the better of Mr. Ishii by killing him, having impaled him in the chest with a sword before piercing the back of his skull or head with the same sword seconds later after Mr. Ishii had bled all over the living room with Mr Ishii dying seconds later.
Seconds later, Matsumoto dragged Mrs. Ishii over to the bed which happened to be the same one nine year old O-Ren was hiding under and then killed her by piercing her heart and chest with the same sword that had killed Mr. Ishii. The sword after going through Mrs. Ishii's chest missed young O-Ren by about an inch, arriving at just a few meters away from her right ear and after O-Ren called for her mother, blood emerged, landing on O-Ren's face.
Matsumoto and his men later left the house, obviously pleased with themselves while the man who had killed O-Ren's father later used some alcohol and Matsumoto's leftover cigar to trigger a fire which ultimately burnt down the house, destroying any evidence connecting Matsumoto and his own men to the horrific crime.
O-Ren managed to get out in the nick of time but was ultimately left psychologically and emotionally damaged at having witnessed the brutal killings at such a young age which led to her swearing revenge against Matsumoto.
Two years later and now at the age of eleven, O-Ren, knowing that Matsumoto was a pedophile and having undergone intense training in preparation crept for the moment in which she would exact her revenge into Matsumoto's private quarters and proceeded to torture him by impaling him in the chest with a sword and she gleefully watched as the pain took its toll on Matsumoto's body with his teeth even being shattered by the torture.
O-Ren then viciously removed the sword from Matsumoto's chest and was drenched in his blood, watching as Matsumoto then died seconds later.
Two of his bodyguards then came to investigate with O-Ren killing both men before fleeing, having successfully avenged her parents but this also marked the beginning of O-Ren's own descent into the Japanese criminal world.
As a crime boss, Matsumoto was a psychopath or sociopath who spared no mercy or remorse for his actions whatsoever.
He also appeared to be a sadist as he was seen laughing manically after O-Ren's father was killed.