Kotomine Kirei

SPOILERS BELOW

Kirei is very sly and can be pretty manipulative, as nobody knows what he is thinking. His manner of speaking is very frank and to the point when not trying to conceal something, with a hint of arrogance and condescension in his voice. At the same time though he never speaks in casual language and never curses or anything like that, and speaks with little passion in his voice (unless he is doing something sadistic). Even when he's engaging in the cruel activities that he finds joy in, he does seem pretty calm but extremely amused.

Kirei as mentioned is the definition of a sadist, though there's a hint of bitterness that extremely rarely creeps up, as obviously he initially did not want to be the way that he is.

Kirei also just gives off an unpleasant aura that makes people dislike him even before he does anything, and even Tohsaka who Kirei essentially raised does not like him. Almost everyone who comes into contact with him wishes that they would never see him again, even when he doesn't reveal his true side.

Though while seeming like someone you'd never want to talk to, Kirei will almost always give information about the grail war when asked, because that is his duty as the overseer. Though when he is fulfilling his duty, he always seems disinterested and simply to-the-point.

Kotomine Kirei is the fake priest who is in charge of the Holy Church in Fuyuki City, and oversees of the 5th Holy Grail War.

His job is to help those who are no longer participating the war and ensure that the war doesn't get too out of hand. He is also an Executor of the Holy Church, meaning he specializes in hunting down mages and other things considered "otherworldly". He also uses the martial art Bali Quan, and uses the weapons "Black Keys", blades that can be held in between each finger (4 is the max) or also be thrown as well.

MAJOR SPOILERS START NOW.

However, Kirei also has a secret much more sinister side; he is someone who does not feel joy when doing morally god things, and only feels joy from sinful actions. While he initially struggled with how he should handle his life, he eventually decided to give into his wicked impulses and live his life as a sinner, even though he was brought up with the teachings of god instilled into him.

The moment he made his switch into giving into his desires was when in the 4th holy grail war, he murdered his long time ally Tokiomi Tohsaka and made a contract with Tokiomi's servant Gilgamesh (and Gilgamesh was also the one who egged on Kirei to embrace his true desires).

Really quick to explain the holy grail war, it's where 7 masters and 7 servants (where servants are historically relevant heroes who each serve a master. an example of a servant would be King Arthur) fight each other to the death until one servant remains, upon which the master with that servant will receive the Holy Grail, which can grant any wish they desire.

To give some more detail on Kirei's past, he was born to Risei Kotomine during a pilgramage. He grew according to Risei's expectations, showing morals and insight. However, he did not love his father, and did not cherish the same morals as normal people.

Realizing this, he tried to correct himself, attempting to be pure. But he could not overcome his defect, as he lacked goodness in his heart from that start. He turned to God, believing that it would give him salvation and save even him. Yet even following the Church's teachings, he could not find what he needed.

His final attempt to change himself was to love a woman, believing everyone wishes to have a family with the opposite sex and die peacefully. He married Clauda Hortensia, who was terminally ill with only a few years left to live. He tried loving hher, and she did love him, and they even had a child, Caren Hortensia. But even so, he hadn't changed, as he felt pleasure from her suffering. Even though Claudia understood him beyond anyone else, she couldn't fill the void within him.

Realizing he could never change, he planned to kill himself. As he was going to inform his wife of this, she tried a final attempt to prove Kirei loved her, by taking her own life, believing her death would make him sad. She saw him crying and so was happy, but in reality Kirei was crying because it meant he could not kill Claudia himself.

But he didn't want her death to be in vain, so he ceased pursuing salvation, though not yet embracing his evil side.

He then was drafted into the 4th holy grail war to basically assist Tokiomi Tohsaka. However, as mentioned, here he ended up embracing his true nature and killing Tokiomi, and having Gilgamesh as his servant. One person to note is Kiritsugu Emiya, who Kirei considered the strongest master going into the Holy Grail War.

Kirei was interested in Kiritsugu because Kiritsugu seemed to be like Kirei; a callous man who did not care for others. However when Kirei realized Kiritsugu was actually very human, he was very disappointed and lost all interest in Kiritsugu.

Though at the end of the 4th holy grail war, Kiritsugu and Kirei engaged in a fight, and Kiritsugu shot Kirei through the heart. However, because he was submerged in the holy grail's mud, his heart was restored, and he had power to control the corrupted mud.

After the war, he became the guardian of Rin Tohsaka, Tokiomi's daughter. Even though Kirei helped Tohsaka and teached her a lot of things, Tohsaka still can't get a read on his true nature and doesn't trust him at all.

In the 5th holy grail war that Kirei overseed, he took great interest in Shirou Emiya, as he was the son of Kiritsugu. While Kirei was supposed to only oversee the war, he ended up directly participating in it. He killed one of the masters (Bazzett) who he was acquanted with from past battles, and forcibly took her servant Cu Chulainn (of the class Lancer), ordering him around to do Kirei's dirty work. He also still has Gilgamesh as his servant after the 10 years that passed between the 4th and 5th wars. In his basement he also stores orphans of the fire that occured at the end of the 4th holy grail war (and he caused this fire). Their life force feeds Gilgamesh.

Kirei and Gilgamesh also have an interesting relationship in that Gilgamesh despite being the more narcissistic dude ever, talks with Kirei pretty casually because he finds Kirei so entertaining and interesting, while Kirei seems to show no fear at all for Gilgamesh's immense power.

He also doesn't like Zouken Matou cause fuck that old man.

Shirou and Kirei while initially seeming like they hate each other, eventually develop a twisted liking towards each other, as both are basically empty human beings in pursuit of happiness. However, while Shirou can only be happy when helping others, Kirei can only be happy through other's suffering, like two sides of the same coin.

Interestingly, it is revealed that when the holy grail has a victor, it will not grant a wish to the remaining master, but instead will give birth to all the evils of the world, Angra Mainyu. Kirei actually wants Angra Mainyu to be born, because he wants to see how Angra Mainyu, a being that is guaranteed to be completely evil, will react once it is born. Will it agonize over its actions, or accept the atrocities it has done nonchalantly? He wants to know if it's wrong to pursue your own desires even if they're evil.

Kirei also LOVES mapo tofu, eating great amounts of it.