Saito Onigiru

Saito Onigiru is the father of all thirteen of the Onigiru children. He had multiple wives who he did not care for at all.

Saito is the current Oni king, leader of all the Oni's, but is specifically the leader of the Onigiru clan. In japan, he is a famous samurai whose known as the "dark knight" and is also a doctor, using a different appearance.

Appearance
According to Kasaida, Saito is over 2000 years old.

He is portrayed with pale skin, long white hair and gold eyes. In his Ryhart disguise, his hair is blonde and he wears glasses.

Personality
Saito is one of the most powerful Oni's in the world, viewed by the Onigiru Clan as a "god". He holds an enormous amount of magical power and knowledge, and he never stops pursuing more.

Saito is extremely intelligent but also very manipulative, and even though he possesses great physical and magical powers, rarely dirties his hands on his own, usually manipulating the others to do his bidding.

Saito is incapable of affectionate feelings and doesn't understand love at all even for the frames of his demonic sub-species. He thinks that just like him the others from the demon-kind cannot feel true love either and therefore starts to admire and glorify the human way of feelings even if he is incapable to feel them himself.

Saito views his wives as test subjects for his experiments in creating a new race, and also his children from them too. He uses everything to his advantage and views his family solely as tools for his utopia goal of a "new race" that he wants to replace the current demons, believing this is the only way for that world to be "saved". He does, however, show an obsession for Kasaida, his youngest daughter, shown by him tearing away all the pictures of him with his previous wives and children, but spared the picture with Kasaida and her mother in it.

Saito also appears to be charming and great at manipulating women, promising them everything until he obtains them, as he does to Shota in wanting to use her as the last remaining First Blood woman. He courts her from very early age and hides from her her true heritage, even though her existence was part of his plans. He gives her false love and spoils her until she becomes his and then starts to mentally abuse her and push her to her limits in order for his experiments of cross breeding and then later wanting to use her heart in a human vessel.

Saito is very strict and cruel to his children, and even though he is neglecting them completely through their childhoods, he can order for their punishments if they do something that displeases him. Therefore and mostly because of the neglect and emotional abuse Saito dealt to their mothers, most of the Onigiru hate him deeply.

Saito becomes more and more fascinated and obsessed with the humans during the years, while punishing his own kind for their own nature, even though he realizes they are that way because they have his genes.

As Ryhart and Uzunami, he appears as a friendly, open-minded and ambitious man.

History
According to Kasaida, he would like to die, but no one is strong enough to kill him. Kasaida would like to fulfill his wish to die. Reiko once says that Saito was only pleased with Kasaida, much to Kazuko's agitation.

Wanting to provide more option for his experimentation, he decided to have children born out of incest. He deceived his cousin, Aiko into thinking that he loved only her and was merely using the other nine women. Aiko, having thought that Saito truly loved her as a woman, willingly agreed to marry Saito and allowed him to have relations with her. When Aiko found out about his experiments, the strong feelings of hate and love, even if he was her cousin, caused her to tear apart and turned her insane.

As revealed by Saito, everything he did towards his wives was on purpose. He made their lives miserable in order for them to break their own children. This is because it was inadequate for the experiment to hinge solely on genetics, and therefore the next stage was to make his wives break their own children in order for his children not to make proper demonic bonds.

Aiko Onigiru
Aiko is actually Saito's cousin. Aiko was revealed to have believed that Saito loved her, and thus agreed to marry him. However, when she realized that she was used to produce children born out of incest, the conflict between her love and hate for Saito drove her insane.

She is constantly seen calling for her 'nii-sama' during her psychotic episodes, and as a result needs Kasaida to calm her down.

Kasaida Onigiru
Kasaida is the only one of her siblings who doesn't hate her father but rather respects him. In turn, however, Saito has a deep obsession with Kasaida, that goes beyond the level of family love. He is so obsessed with her that he has killed many people who abused her, mistreated her and called her names without mercy. He is only ever pleased with her and anything involving her. His obsession with Kasaida grew to escalating proportions to the point that he was willing to harm those whom he believed would take Kasaida away from him, be they friends, rivals, relatives, other men, etc. At one point he even kidnapped Kasaida and held her hostage because he was so terrified that another person would kill her. Reiko has stated that Kasaida provides a stabilizing influence in his normally chaotic and violent life.

It is shown many times in the series just how deeply insecure Saito truly is when he says his life would not be worth living if he could not be the center of Kasaida's world. His crippling fear of losing her is notably the only thing that can cause his usually disturbing composure to crack.

Abilities
Saito possesses all the racial abilities of a pure born Oni. He also possesses the highest level of magic in the Demon World. His power is considered by his race and his children as “God-like”.

He is the creator of the “eternal flowers”, and also the one that creates a new race of cross-breed between humans and demons. Saito’s unleashed magic can destroy the Demon World, setting it on fire and killing most of the inhabitants there.

The only way to kill him is through cutting his head off or stabbing his heart.

Shape Shifting
Saito is seen to be able to shape shift and change his appearance to any look he wants. According to Fumiko, he can be a man or a woman, any appearance is possible. Said by Keiko, he appears in a different form sometimes. They don’t actually know what he really looks like.

Trivia

 * The meaning of Saito is "purification wisteria". The most common Kanji used in the name Saito is 斎藤. The name meaning could vary if alternative Kanji are used.
 * The surname Onigiru likely stems from the name Oni, meaning "He (God) has favored me", with Giru being a possessive particle.
 * His theme song is titled "Daddy's Home".