Tōga

Great Dog Demon (犬の大将, Inu no Taishō) was a powerful yōkai lord who was known throughout Japan. Never formally addressed with a name, he fathered two sons by two different mothers: Sesshomaru from an unnamed dog demoness, and InuYasha from a human woman (unnamed in the manga, but named "Izayoi" the third movie). The Great Dog Demon is first mentioned in chapter 12 of the manga as InuYasha's father, "a demon dog that prowled the lands of the west". The Great Dog Demon's major foe in the manga was the dragon Ryūkotsusei, whom he could not kill but sealed onto a cliff face with his claw; Myōga calls this battle the "cause" of his death. In the third InuYasha film, InuYasha the Movie: Swords of an Honorable Ruler, the Great Dog Demon survives long enough to save Izayoi and their newborn child InuYasha; still weak from his battle with Ryukotsusei, he dies defending them from a human foe. The gateway to his tomb is hidden in a black pearl (a mystical gem that creates a path between the mortal and spirit worlds) inside InuYasha's right eye. Within the pearl, their father's body is shown as an enormous dog skeleton in a suit of armor: his true form, according to Myoga. The sword Tetsusaiga, forged from the Great Dog Demon's own fang, rests inside this cavernous skeleton, protected by a barrier that repels any non-human with malice toward humans. Because of this, InuYasha inherits the sword rather than Sesshomaru.

Abilities
Much of the Great Dog Demon's abilities are unknown, but it is known that he could change his appearance into a human looking form similar to Sesshomaru and his former mate. His true form was that of gigantic dog which far larger then both Sesshomaru's and Sesshomaru's mother's true yokai form allows him to move at top speed. He has been stated to be one of the most powerful yokai in the series by Myoga and Totosai. Despite his great power he was unable to kill Ryukotsusei and was only able to defeat him by sealing his powers away. The aftermath of the battle lead to the dog demon's death. Both of his sons Sesshomaru and InuYasha surpass him.

Relationships
Sesshomaru's Mother: She was his first wife and had Sesshomaru as a child but left her for Izayoi. Though she was not seen or mentioned in the anime she was seen in the manga and she might appear in The Final Act. Such as also being a Daiyokai like her husband, she can also transform in to a gaint dog which was also passed on to her son.

Izayoi: It is unknown when they first met but they end up falling in love and the result is Inuyasha. After his last battle, he rushes to save her without first tending to his wounds. He fights through the soldiers only to find her already dead. Using the Tenseiga, he brings her back to life, giving her the Cloth of the Fire Rat, and telling her to escape with their newborn son whom he calls InuYasha. His last words were: "Izayoi...You must live. Live a long life. Live long [and] well with Inuyasha."