Updated with Manga Spoilers through the Kakashi Gaiden . Do not read unless you want to know or already know the details of Kakashi's past:
Case Study of Hatake Kakashi
Subject's Background (Updated):
Hatake Sakumo, subject's father, aka White Fang, was a genius ninja on par with the legendary sannins. He abandoned an important mission to save his comrades, after which he was blamed and disgraced even by those he saved; and thus committed suicide. Kakashi was about 8 years old when he bore witness to this tragedy.
After his father's suicide, Kakashi started to adhere strictly to the shinobi rules, in particular, the rule dictating that the mission must come first. He became arrogant, humorless, and by-the-book. Kakashi achieved jounin status at 13 years of age. There was no elaborate ceremony. Instead his reward was to lead his team on a sabotage mission to blow up a bridge in order to prevent forces from Earth Country from entering Grass Country.
His teammates were Rin (a female medical ninja), and Uchiha Obito. In the course of their mission, Rin was captured. Kakashi ordered Obito to continue the mission, but Obito disobeyed his commander to rescue his teammate. Obito reminded Kakashi of Sakumo's decision. Obito considered Sakumo a true hero. Obito's remarks caused Kakashi to reconsider his own priorities.
Kakashi lost his left eye while protecting Obito and his scar is a result of that injury. They were able to rescue Rin, but were again attacked by the enemy whereupon Obito sacrificed himself to save Kakashi. Upon his death, Obito bequested his left eye to Kakashi to replace the one he had lost.
The impact of a parent's suicide on a young child of eight, no matter how hardened by war and death, must be devastating. Hatake Sakumo was respected on the order of the legendary sannins, and for him to fall from grace at such a great height would have profoundly affected his entire clan. His disgrace was not only borne by himself, but also by his family, and most directly by his son, Kakashi.
What would push someone past his natural instinct for self-preservation to suicide? In the Western culture suicide is normally a manifestation of mental illness and depression. In Sakumo's case, it was said that his mind and body became weak, but it was possibly an honorable way to redeem himself and his clan from ignominy. Ritual suicide, seppuku, was a key part of bushido, the code of the samurai warriors. Seppuku was an act of bravery that wiped away transgressions, and enhanced the deceased's reputation. Sakumo may have resorted to this desperate attempt to restore his and his clan's honor. But after the tragedy, Kakashi never spoke of his father, probably due to the shame and stigma of suicide in addition to the humiliation suffered from his father's questionable decision.
A consequence of Sakumo's suicide on his young son was Kakashi's newfound fixation on following the rules. His father would not have been disgraced if only he had followed the rules and completed his mission. Kakashi came to believe that the mission was of foremost importance and his teammates were expendable. But five years later this belief was challenged by his "best friend" Obito.
Uchiha Obito was the great influence in Kakashi's life. Although in adulthood Kakashi calls him his best friend, in actuality, their relationship was adversarial. They were like "oil and water" where Kakashi was the serious genius from a disgraced clan, and Obito was the buffoon from an elite clan, the Uchiha with the advanced bloodline sharingan capability. The bitterness that Kakashi felt after his father's death was probably exacerbated by being paired with someone from such a respected clan as the Uchiha.
Envious of Obito's bloodline, and disgusted with Obito's lack of gravity, Kakashi appears to have gone out of his way to insult the Uchiha at every opportunity – an exhibition of transference of anger towards his father to his rival. Sakumo's suicide was ultimately a selfish act, leaving behind a young son to fend for himself. Survivors often feel guilt that they should have done something to prevent the suicide, anger at the person for leaving them, or anger at others for causing the suicide.
In contrast to Kakashi's belief, Obito cared for his teammates above all else. His words finally awakened Kakashi to the impossible decision his father had to make on the spur of the moment: save his comrades from certain death, or complete the mission, failure of which could possibly lead to even more deaths.
In the end, the two reconciled as friends. But whether Obito hated Kakashi or cared about him was not a conscious consideration when Obito pushed Kakashi out of the way of the falling rocks. Yet Kakashi grants Obito the adulated status of "best friend" despite their not having been friends in the conventional sense. Kakashi's survivor's guilt, heightened by Obito's sacrifice, and by the fact that he had treated Obito shamefully, results in denial of their true adversarial relationship.
These circumstances also gave rise to introjection, another defensive coping mechanism. Introjection occurs when an individual deals with emotional stressors, such as guilt, by internalizing the values or characteristics of another person; usually someone who is significant to the individual in some way. Whether conscious or subconscious, over the years, Kakashi has gradually assumed facets of Obito's personality in order to keep him alive: he's often late; he makes up pathetic excuses; and he exhibits inappropriate levity.
At first glance, Kakashi exhibits a diametric personality. On one hand, he seems lazy and nonchalant, not caring how others perceive him. On the other hand, he is arrogant and serious, a respected leader. But all these characteristics are actually expressions of an innate need for control.
The uncontrollable events in his life could have prompted the young shinobi to be obsessed with control. Prior to Obito's death, Kakashi already exhibited control behavior: He was competitive and bullied Obito; He was stubborn and arrogant, as demonstrated by his insistence on using his chidori against Yondaime's advice.
Kakashi as an adult, not only controls his emotions, but also how people perceive him. The mask creates an aura of mystery and privacy. The scandalous books read in public creates an image of a perverted buffoon, contrary to his original character and more like his deceased friend's personality. Yet despite often being called an idiot, in serious occasions, he rises to the forefront as a respected leader in control of the present situation as other jounins look to him for leadership and advice.
For Kakashi to lose control, especially of his temper, is a rare event. A prime example of how loss of control affects him can be seen in his encounters with Kabuto where Kabuto is in charge of the situation. In their first encounter, Kakashi resorts to his usual arrogance and sarcasm to assume charge, but Kabuto is unfazed. After Sandaime's death, Kabuto taunts Kakashi whose hand then uncharacteristically shakes in fury at his own inability to do anything.
Sakumo's suicide and Obito's sacrifice were the primary events that molded Kakashi's adult persona: An anti-social, private man, who would rather have people think he's a lazy idiot like his purported best friend, rather than reveal his true nature. Whether the subject himself knows his own true nature is questionable; the subject has a distorted self-perception. In his self-examinations, Kakashi finds himself contemptible, despite truly being one of the great heroes of Konoha.
Author's Notes: I did not change the original article since even though some of the inferences were wrong, I think they were interesting.
Psychological terminology and definitions, and information on seppuku were taken from Wickipedia.
More on Sakumo in my "Excerpts from Kakashi's Diary" stories.
Written in the hopes that people will write In-Character Kakashi stories where he doesn't get drunk and jump Iruka's, Anko's or X's bones!