In his human form, Tohru's father appears as a middle-aged man with grey hair and a beard. He wears a reddish-black cloak that he can transform into wings.
In his dragon form he is a large red dragon with reddish-black wings, and a white mane, beard, and moustache-like whiskers.
Tohru's father is callous and stern, hating humans and viewing them as inferior and evil - a belief he tried to impart on Tohru. However, unlike other Chaos Dragons, he respects the non-interference laws preventing dragons from killing humans of Earth - although when angered he attacks Kobayashi and threatens to leave her at the brink of death. Despite this, he cares for his daughter and is concerned for her safety, warning her that the peaceful human life she claims to want is impossible, and that her presence risks bringing the war between the Chaos and Harmony faction dragons that is ravaging the Other World to Earth. In the manga, he leaves after Tohru intimidates him, while in the anime, he strongly disapproves of Tohru's choice of mate, but accepts her decision and leaves her in peace.
In the manga, Tohru's father shows up on Kobayashi's doorstep to demand Tohru return home to the Other World. When Tohru refuses, he explains to her that the peaceful human life she desires is impossible, and that sooner or later she will be found out or lose control of her bloodlust, and that even if that does not happen Kobayashi's lifespan is miniscule compared to hers. Further repremanding her for breaking the non-interference laws, he warns her that her presence risks drawing other dragons to Earth. When Kobayashi mocks him, he attacks her but is stopped by Tohru, who intimidates him into leaving.
In the anime, Tohru's father is given the title of the Emperor of Demise, and approaches Tohru while his daughter is struggling with the realization of Kobayashi's mortality. The Emperor of Demise returns Tohru to the Other World, and when she returns several days later, he confronts her over her defiance. When Kobayashi tries to interrupt their argument, he destroys her glasses and threatens to leave her on the brink of death unless she chooses her words carefully. When Kobayashi's speech restores Tohru's resolve, the Emperor of Demise challenges her to a battle, opening a portal to an isolated area. Their fight is interrupted by Kobayashi and Kanna, who urges them to reach a compromise. While he refuses to approve of Tohru's choice of mate, the Emperor of Demise decides to respect her decisions and returns to the Other World.