Byakuya Matou

Byakuya Matou (間桐 鶴野) is a posthumous character. He is the older brother of Kariya Matou and father of Shinji Matou.

Appearance
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.

Personality
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 believes he is following the right path for the future of the Matou family. Byakuya despises Kariya, for leaving the family (believing that because of it, he had to endure the cursed destiny of the family) and Sakura, because he was forced to stay in the Matou house to train her. He does not care about what happens to the family, but he does care for his son, as he tried his best to hide the truth from him about Sakura's status as the heir apparent, but after Shinji later founds out the truth out of curiosity, he becomes distant with him.

In the Drama CD, he comments that he was neglected by Zouken due to his few circuits since childhood, which might be the cause why he wanted to hide the truth from Shinji in the first place. 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 Shinji.

Background
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 spent a comfortable and carefree life, however the stress was too much and he became an alcoholic as a result.

Fate/zero
"Kariya? I don't know where that fool is!"

- Fate/Zero, Episode 21

He is responsible for sending Shinji away to study abroad. Alongside Zouken, he trains Sakura at the worms storage,and because of this Sakura despises them both. 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 him, 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.

In the novel, Kiritsugu shoots at Byakuya's hand, making it disappear (while in the anime, he simply injures his hand and leg) and after realizing that Byakuya doesn't know where is Irisviel, he leaves a terrified Byakuya crying.

Unlimited Blade Works
"You are the only hope of the extinct Matou bloodline. Do you understand, Sakura?"

- UBW Manga, Chapter 29

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. Shinji claims he resents his father, because he is a failure and for "not chosing him".

In the manga version of Unlimited Blade Works, he 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 (unsuccesfully) from knowing the truth about Sakura, similar to the visual novel. 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, becoming harsh with her.

Heaven's Feel
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 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 (who had been hiding the truth about Sakura from him) 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/hollow ataraxia
Byakuya (alongside Kariya and Zouken) were mentioned by Shinji, saying that they all sulked about their lives because they were Matous.