Fate/Zero is a series that tackles a multitude of broad psychological and philosophical themes through its characters and their respective conflicts. These articles will be spoiler filled, and if you haven’t seen Fate/Zero yet then I recommend that you read my review and watch it (it is also available on Australian Netflix) before continuing. This week, I will be discussing how human empathy and the nature versus nurture argument is explored through the rivalry between Kiritsugu Emiya and Kirei Kotomine. These are based on Fate/Zero as a stand-alone, so any contrarian or supporting evidence presented in any other Fate series will not be considered.
Kirei Kotomine, presumably since he was born, has implicitly exhibited the qualities of a psychopath, although that’s not to say that he’s to blame. He tried to follow everything that his father said, believing that it would fill him with the same feeling of self-worth as it did seemingly everyone who worked in his organization. However, his lack of empathy that both contributed to, and followed, the death of his wife and the omnipresent feelings of (unexpressed) disinterest in dogmatically mimicking those around him and carrying out the orders of the church did not produce any genuine sense of value. He attempted living straight-laced and honest, making connections with all the powerful and influential circles and training until he was nearly invincible, all of which failed to grant him any true happiness. He was a psychopath by nature, and his father, who had an evident lack of interest in his son doing anything besides upholding the family tradition, may well have never considered getting to know him (this ties into the theme of family, which will be discussed later). Kirei would never speak up because of his belief that obeying the commands of the church would grant him happiness, and the devout Risei Kotomine, with similar family values to Tokiomi Tohsaka, evaluated the success of Kirei’s life by his combative prowess and ability to memorise verses, not by how fulfilled he felt.
This brings up an interesting dilemma; had Risei ever taken the time to get to know his son, there may have been a chance that Kirei could have had his lack of interest addressed. However, Risei’s devoutness and lack of interest in Kirei suppressed his sense of self, leaving Kirei to gradually grow bitter with his murderous tendencies hidden even from himself due to his lifestyle. Psychologically, it’s easy to see how the prioritisation of the church and prestigious families over Kirei’s emotions may have led to Risei, Tokiomi and everyone else missing Kirei’s condition. Typically, psychopaths have a tendency to be manipulative, superficially charming, and display indifference to acts of love or violence; all the things, in short, that Kirei is taught not to do from a young age both directly and through observation. He may be considered a villain by nature; the only guidance figure who ever really knew Kirei was Gilgamesh, and it’s obvious that the King of Heroes was much more in tune with Kirei’s deepest desires than Risei ever was. When Kirei manipulated Kariya into strangling Aoi, taking advantage of a man who took on brain damage to save a poor girl, he was genuinely pleased with himself, and in just one scene ticks off close to every box in the psychopathic checklist. However, is he really the only one to blame, or should Risei be held responsible for never really knowing his son? On the whole, he was simply doing what made satisfied his conscience, determined by genetics and perhaps enforced by oppression, willed him to do for satisfaction. He tried to follow what most consider the “objectively” right path for his entire 27 year life span till the 4th Holy Grail War. Though by the logical of his thematic parallel, his justifications are irrelevant.
“Psychopaths are just people. You are right to say that psychopaths hate weakness, they will attempt to conceal anything that might present as a vulnerability. The test of their self-superiority is their ability to rapidly find weaknesses in others, and to exploit it to its fullest potential.” 
Kirei is an example of nature overcoming nurture, which brings us his major contrasting character of Fate/Zero, Kiritsugu Emiya. Kiritsugu was brought up in a coastal community with many other people his own age, having healthy friendships with those around him and even a potential blossoming romance. However, through his relationship with Natalia and observations of how preemptive strikes against the few can save the many (given his inability to Shoot the Dog was what led to his community’s slaughter) he became a bonafide utilitarianist. Sure, it can be argued that initially he was thrust into a world of darkness and magic through no choice of his own, but the way in which he acted against his primal nature, tearing out his soul so that others may no suffer and embodying the spirit of a Byronic Hero certainly paints most of the choices he made in his adult life as his own.
While Kirei tried hard to go against his nature as a sadistic psychopath, the lack of therapy in the early stages of his life and apparent parental disregard for his emotional well being left his nature to build under pressure rather than fizzle out. Kiritsugu, on the other hand, built his own justifications to being a killer for the sake of many, his bright eyed optimism dulling heavily as a result of Natalia’s influence and his own constructed perception of the world and the correct way of fixing it. However, he never really could refute his ultimately good nature in the long run, as the grail depicts that he genuinely loved Irisviel and Illya, so much so that it was his implicit desire to keep them safe, even if it goes against his self-taught principles. Herein lies one of Fate/Zero’s brutally nihilistic ends; both men tried to overcome their nature to find what they desired (self-worth for one, world peace for the other) by going against their nature (that of a sadistic serial killer and family man) as a result of what they evaluated to be the right things to follow (the teachings of the church and utilitarianism). In the end, Kiritsugu’s inner desire to protect his family meant that his utilitarian principles would only bring him heart break, while Kirei’s unchecked psychopathy prevented righteousness or acts of kindness from ever carrying any weight to him, so both men’s actions failed in giving them the satisfaction they required. Both of these men have ambitions and natures akin to two powerful magnets of identical polarity being forced together, with Kirei’s Catholicism and Kiritsugu’s utilitarianism contrasting the cores of whom they are far too strongly to have ever worked.
Another area where Kiritsugu and Kirei were similar was in how their development was stunted. In Japanese, Kiritsugu constantly refers to himself as “Boku”, which is unusual for adult males, reflecting that guns and whistles aside, Kiritsugu is a man child who hasn’t changed since the basic principle of utilitarianism and planning was drilled into him at a young age. Much like Light Yagami of Death Note, his logistic and strategic prowess doesn’t compromise what is, at its core, an uncompromisingly holistic and emotionally shallow philosophy of saving the many in exchange for the few. However, Fate/Zero covers this much better by presenting Kiritsugu’s shock as a result of his past and determination. Kirei, meanwhile, seems to have been the way he was in during the events depicted for quite some time beforehand, given how everyone misinterprets his dissatisfied lack of emotional involvement as professional minimalism. This isn’t quite water tight, though; given that Kirei is an executioner, wouldn’t he have noticed his tendency towards violence and confessed? Plausibly, something like that may have occurred in the past, but it certainly isn’t noticeably addressed here.
Nihilism ultimately won out in the end, as is a running trend throughout Fate/Zero. As Gilgamesh brought out Kirei’s inner sadist, he ultimately had nothing to lose; he was prepared to set his life on the line to discover what about himself left him at odds with what he was taught was good and true. He would probably have gladly given up his father’s church, everyone and everything he had ever met and even his own soul for an answer. Kiritsugu, on the other hand, valued his family more than the faceless masses (as the grail displayed), and his utilitarian principles juxtaposed his primal emotions to the extent that he would have great difficulty sacrificing them for the sake of many. The solution should have been obvious to the beginning to these two men; Kirei could have been a serial killer and lived out his days as a tempest of chaos, and Kiritsugu should have devoted his life to protecting his family, the subjective “ones who matter”, as the many would always be in danger, no matter how often Kiritsugu would avert a major threat.