|“||Kariya? I don't know where that fool is!||„|
|~ Byakuya Matou, Fate/Zero Anime Episode 21|
Byakuya Matou is a posthumous villain from the Fate series who is the older brother of Kariya Matou and father of Shinji Matou. He appears in Fate/Zero and is dead by the time of the events of Fate/stay night, having died three years before then.
Byakuya has curly blue hair, like his son, but unlike him, he has it in longer bangs that reach his eyes. His clothing consist in a white shirt and a black suit.
Due to being considered as a disgrace to his family, Byakuya is a depressed, broken alcoholic. He is the one who supervises Sakura's training at the underground worms storage. He knows that he is just being used by Zouken, but he is resigned about it (however, he tries to believe that he is following the right path for the future of the Matou family). Byakuya blames Kariya for all the pressures he must now face as the family head. He also loathes Sakura, because he was forced to stay in the Matou house in order to train her.
Byakuya hates everything related to magecraft and does not care about what happens to the family. The only exception was, apparently, his son Shinji, as Byakuya tried his best to hide the truth from him about Sakura's status as the heir and about the existence of the worms storage. Unfortunately, after Shinji later founds out the truth, Byakuya becomes distant with him.
In the Drama CD, it is revealed that Byakuya was neglected by Zouken due to his few circuits since childhood. Byakuya is prone to sulk about his disgraces when he is drunk and can be depicted as a haughty character, but later when Kiritsugu attacks him, he shows cowardly and even pathetic qualities, just like his son.
When he was young he was passed over as heir to the family due to possessing very few, if any, magic circuits. Because of it, he was neglected by Zouken and due to it, Byakuya grew to resent his younger brother and more magic-capable, Kariya. Because Kariya refused to be the heir and a pawn for Zouken's plans, Byakuya had no choice but to become the next Matou family head. In later years Byakuya would meet a woman with an "inheritor" sorcery trait and marry, resulting over all in the birth of his son, Shinji. Unfortunately, Shinji was incapable of sorcery, making Byakuya even more of a disgrace to his family for not producing a worthy heir. Due to the failure, his wife was thrown to the worms storage where she later died. This would eventually result in Zouken adopting Sakura Tohsaka as the new heir to the family. Byakuya was completely aware that he wasn't really the head of the family (since everything was orchestrated by Zouken) but he decided to live a comfortable and carefree life, however the stress was too much and he became an alcoholic as a result.
He is responsible for sending Shinji away to study abroad (it is implied that he did it because he did not want his son to get involved). Alongside Zouken, he trains Sakura at the worms storage. After Irisviel was kidnapped by Kariya and Berserker, disguised as Rider; Kiritsugu goes to the Matou house, when he confronts a drunk Byakuya. Believing that he knows what happened to Irisviel, Kiritsugu shoots Byakuya's hand, making it disappear which terrifies Byakuya and causes him a breakdown. After realizing that Byakuya doesn't know where is Irisviel, Kiiritsugu leaves him crying.
In the anime, Kiritsugu injures his hand and leg, only for a scared Byakuya to tell him that he has no idea where Irisviel is located, but he later declares that Kariya was last seen off with Kirei.
Unlimited Blade Works
In the route it is revealed that Byakuya wished to finish off the Matou blood, unlike Zouken, who wanted the revival of the family blood by adopting Sakura. Byakuya tried to keep the awful truths of the heir of the family and the worms storage away from Shinji, which he ultimately failed after Shinji found out anyway. Ironically after the death of Byakuya, Zouken told Shinji everything Byakuya tried to hide from him, which in turn caused Shinji to hate and resent his own father for not choosing him as the heir.
The Heaven's Feel scenario reveals more details about him. Zouken considered Byakuya and Shinji as disgraces to the family and that Byakuya spend the rest of his life living meaninglessly. He is shown to have collaborated with Zouken in Sakura's cruel training, being revealed that he hated Sakura and he enjoyed watching her suffering (It is also implied that he collaborated with Zouken in poisoning her food).
He is also mentioned in Shinji's flashbacks. After a young Shinji accidentally entered to the worms storage in which Sakura was being infested by the worms, Byakuya started acting distant and defiant towards his son and started spending more time with Sakura. Thereafter, Byakuya gave up on hiding the truths of the family from Shinji and died a few years later before the events of Fate/Stay Night. With Byakuya dead, Shinji realized he was alone and ignored by everyone in the Matou house, since Zouken was more interested in training Sakura.
Fate/stay night Manga
|“||You are the only hope of the extinct Matou bloodline. Do you understand, Sakura?||„|
|~ UBW Manga, Chapter 29|
In the manga version of Fate/stay night (which follows the Fate and Unlimited Blade Works scenarios), Byakuya appears in Shinji's flashbacks although his face was never clearly shown. Since Zouken does not seem to be present in the manga, he is the one who adopts and trains Sakura.
His relationship with Shinji is unknown, but it also seems that he tried to protect him (unsuccessfully) from knowing the truth about Sakura, similar to the visual novel, even going as far as also hiding Shinji the fact the Matou family is a family of Mages. Ironically it was Byakuya's actions that made Shinji find out the truth eventually. Out of curiosity, a young Shinji followed Byakuya to the study, during which he later found out that his family was a family of mages. He would later overheard a conversation between Sakura and Byakuya in which he found out the reason why Sakura was adopted into the family. It is unknown what happened to Byakuya after that, but he is presumed to be dead.
Byakuya, alongside Kariya and Zouken, were mentioned by Shinji, saying that they all sulked about their lives because they were Matous.