One relationship dominates Sasuke's life, and has done since childhood. The special bond he shares with his brother is the source of his torment, driving him to self-destructive behaviour and a refusal to form other close relationships. Despite wanting to hate him, Sasuke can't deny the power Itachi has over him: everything Itachi says to him, he takes as truth; everything he demands, Sasuke tries to fulfill. The mental struggle Sasuke fights against his feelings for Itachi reveals his darkest secret: Sasuke's only desire in life is for acknowledgment from the brother who betrayed him. This used to be an innocent longing for recognition, but since Itachi left him it has become a guilty obsession, tainting everything he does.

As a child, Sasuke is very proud of his family's reputation as the only clan strong enough to enforce the law. He sees elite ninja all around him, and vows to become strong himself, worthy of the Uchiha name. Where others would measure their abilities against those of their peers, Sasuke is only interested in how he compares to his elder brother, and how Itachi and his father regard him. While Sasuke is naturally talented and comes top of his class, Itachi is a prodigy, graduating years early from the academy and mastering the Sharingan with ease. Sasuke sets himself an impossible task when he fixates on becoming as strong as his brother.

Sadly, their father only appears interested in his first son, taking Itachi's genius for granted and finding Sasuke wanting in comparison. This only further fuels Sasuke's intentions to reach his brother's level, but for a time it seems Itachi is the only family member who pays Sasuke attention.

At that point in time, Itachi is willing to take Sasuke to the training grounds and show him what he has to achieve, but stops short of training him or letting Sasuke copy his routine after him. Young Sasuke would fail to hit all the targets Itachi got perfectly, and the direct contrast of their respective abilities would upset and discourage the younger boy. Itachi protects Sasuke from this by saying there is no time left for him to try it. Sasuke knows it's a lie; Itachi remains firm but gentle with the boy's feelings. This is the only time Itachi shows any empathy with someone else's emotions, and he handles his brother perfectly. Sasuke is too young to comprehend the nurturing support Itachi is providing, but he is delighted to have the companionship of his brother. His feelings soon grow to hero worship, and he wants to be just like Itachi.

Itachi encourages Sasuke's attention, giving him the impression that Sasuke is very important to him, and that he cares more for Sasuke's feelings than his father's. When Fugaku forgets about Sasuke's academy entrance ceremony, Itachi courts his anger by saying he'll refuse a mission, eventually shaming Fugaku into attending the ceremony. This exchange takes place in front of Sasuke, with Itachi giving his brother sidelong glances as he provokes their father, implying an allegiance with Sasuke against him. Sasuke is pleased with the outcome, but this is the first sign of the disintegration of the relationship between his father and Itachi.

Shortly thereafter, Itachi joins ANBU. There is more evidence of the bad feeling between him and Fugaku, and Sasuke is worried and uneasy to discover secret meetings and conversations punctuated by flashes of the Sharingan. As an ANBU, Itachi is now working for the village rather than the clan, and Fugaku can feel his son slipping away from him. His veiled threats to keep Itachi in line seem feeble against his prodigious son, who no longer shares his ideals and has become stronger than the father.

A discussion with Sasuke reveals that Itachi's only goal is to become as strong as he possibly can. He takes pride in his talents and believes the whole point of being a ninja is to push oneself to the limits, even if it means sacrificing friendships. Itachi is so convinced that this is the correct course of action that he expects Sasuke to do the same, indicating that the reason behind letting Sasuke watch his training was indeed to foster the desire in him to become strong. He suggests that Sasuke has potential waiting to be unlocked, and that having Itachi around to encourage him and demonstrate his goal is what Sasuke needs.

This is the scene which reveals most about Itachi's psyche, as he is content with the assumption that Sasuke hates him. How he drew this conclusion is a mystery, as it seems very clear that Sasuke idolises his brother. While he wants to become as strong as him, it's not out of a desire to beat him, but simply because he wants acknowledgement from the two people he most respects: Itachi and his father. He wants to be like his brother, and he wants to make his father proud to recognise him as his son. The only way of achieving this is to become as skillful as Itachi, and that is the force behind his wish for strength.

Itachi doesn't see this, despite being the one who spends most time with Sasuke. He must have built up an idealised picture of Sasuke in his head, projecting his own feelings and responses onto him. Itachi is much stronger willed and more independent than Sasuke, and he would not accept second place easily. Being the second son, Sasuke is constantly reminded that he will have to work much harder than Itachi to match him, and has come to regretfully accept it. He bears no malicious feelings for his brother, but Itachi can only imagine him hating the one he is chasing. This suggests that Itachi's obsession with Sasuke's improvement has blinded him to the reality in front of him.

Sasuke is uncomfortable with his own feelings for his brother, and doesn't know how to respond when Itachi asks if he dislikes him. It would be embarrassing to declare how highly he thinks of him and how much he strives just to gain his acknowledgment, especially when Itachi seems to want him to answer affirmatively. Itachi takes his discomfort for not wanting to hurt his feelings, and the moment for honest disclosure passes. The impression is given of two people who desperately want something from each other, but misunderstand the other's intentions. Despite this, their mutual affection is obvious in Itachi's smiles and Sasuke's confiding air.

If any doubt was left about where Itachi's loyalties lie, the next scene clearly shows he cares only for Sasuke. After police officers hint that Itachi is suspected of murdering his cousin Shisui, a fight breaks out where Itachi makes short work of the three police. Fugaku returns home, sparking an ugly confrontation between the two. Through barely contained fury, Itachi tells his father he doesn't believe in a duty to the clan, and it appears that a fight between father and son is the only possible outcome. Sasuke calls out to Itachi, who immediately drops to his knees to beg forgivness, unreasoning rage melted away. If it had not been for Sasuke's voice bringing him back from the edge, Itachi could have started the clan massacre that day. Possibly his earlier promise to stay by Sasuke's side as a role model returned to him, causing him to defuse the situation.

This confrontation is the turning point in the family dynamics. Afterwards, Fugaku and Itachi don't speak or even look at each other, and Itachi shows indifference to Sasuke. The forlornness he feels at losing his brother's companionship is somewhat offset by the sudden interest his father takes in him. Fugaku cuts Itachi out of his life entirely, and tries to determine if Sasuke will be able to replace him as the strong, loyal son he wants. Sasuke trains hard, and eventually his father acknowledges him. While Sasuke is pleased to finally gain his recognition, he's always aware that he is only Itachi's replacement, never quite breaking free from his shadow.

Sasuke takes no pleasure from his new position in the family whenever he sees the distance between Itachi and his father, and he is deeply troubled by his brother's withdrawal from family life. Really, he covetes his father's acknowledgment of both sons equally and Itachi's attention and friendship. However, it seems the family rift is impossible to heal once Fugaku tells Sasuke not to follow his brother's path. This sets up the ultimate dilemma that plagues Sasuke: his goal is still to become as strong as his brother, and gain Itachi's acknowledgment, but his father explicitly says not to become like Itachi. If he wants to retain Fugaku's approval, he can't become isolated and remote from the clan, but Itachi has told him that stretching himself to the limit will necessarily isolate him from others.

This problem is brought to a head when Itachi massacres the clan, using genjutsu to show Sasuke how he killed their mother and father. As a young boy faced with the corpses of his parents, he is terrified of the calm, dispassionate killing force his brother has become, and runs away begging for his life. Itachi catches up to him, revealing the family secret of the Mangekyou Sharingan, and telling him that he will only acknowledge Sasuke when he stands before him with it.

Itachi's reasons for killing the clan are never made fully clear, but he tells Sasuke that it is for his benefit. Indeed, Itachi tries to spare Sasuke the pain of seeing their dead parents, telling him not to enter the room in which they are lying. By disregarding his warning and asking what happened, Itachi feels Sasuke invites the trauma of having the Mangekyou Sharingan used against him, and sees it as an opportunity for strengthening his little brother. Itachi has watched Sasuke transfer his affections to their father, and sees loyalty to Fugaku and the clan as weaknesses sidetracking his determination to become strong. Additionally, he may feel jealous that he is no longer the only one commanding Sasuke's attention. Showing Sasuke the full horror of the massacre is a reminder of who is the strongest in the clan, and who truely deserves Sasuke's respect, as well as providing Sasuke with a concrete reason to push himself to his limit.

Itachi gives him a new goal: revenge. Out of a twisted sense of doing him a favour, Itachi removes the barriers to Sasuke's development -- the barriers of attentive parents and a peaceful life. Sasuke is devastated by the betrayal of the brother he idolises killing the father he respects, then betraying him further by leaving him. His twin purposes in life become avenging his parents by killing Itachi, and reviving his clan. This is exactly what his father would have wanted, and he can continue to be the good son Fugaku desired by following this path.

However, seeking revenge is also what Itachi wants of him. The stated intent of the massacre was to give Sasuke space and resolve to reach his full potential, culminating in confronting Itachi with Mangekyou Sharingan awakened. Sasuke is deeply, terribly hurt by his brother's actions, but he is only capable of being so wounded because of the strength of his trust and admiration in the first place. He can barely admit it to himself, but he never loses the compulsion for acknowledgment from his brother, and the way to gain it is to become strong enough to defeat him.

Sasuke would tell anyone who asked that he is an avenger, intent on killing his brother. Whenever he's feeling like a good son; whenever he acts like a good Konoha ninja; whenever he talks about his task with anyone, he would say he must kill his brother to avenge his father. When he thinks of Itachi the truth surfaces: he wants to defeat his brother to prove his strength to him and gain Itachi's acknowledgement. This is the dark part of Sasuke that is only revealed in hints; his gluttonous desire for his brother's approval is the real drive behind his quest.

Since Itachi fled Konoha and became a missing-nin after the massacre, Sasuke has many lonely years to brood over his tragedy. Over that time he focuses entirely on gaining enough strength to defeat Itachi, training even harder than he did before and shunning any potential friendships. This appears to be Sasuke following Itachi's orders exactly, but it is likely he is simply afraid of forming new attachments which could be broken. Despite his determined isolation Sasuke's warm-hearted nature breaks through, and he can't help but grow to care for his three teammates. His life settles into a relatively stable pattern of training and performing missions with his team.

He is thrown off-balance when Itachi returns to Konoha. Seizing the chance to prove how much he has improved, Sasuke tries out his newly-mastered Chidori, fueled by wrath from recalling the massacre. Itachi becomes impatient seeing Sasuke with Chidori rather than Mangekyou Sharingan, and quickly defeats him. When Itachi reveals that he returned for Naruto and has no interest in him as he currently is, Sasuke makes another attempt to fight and gain his attention. Itachi doesn't hold back in his counterattacks, using the opportunity to remind Sasuke of his reason for seeking revenge. He also leaves Sasuke some advice: he is still weak because he doesn't hate Itachi enough.

Sasuke's reactions to this incident reveal a lot about what he currently feels for his brother. He is gripped by an overwhelming hatred of Naruto, stemming from envy of Itachi's interest in him. He irrationally feels betrayed by Naruto for becoming his friend and then taking Itachi's attention. This jealousy is so strong that he twice resolves to kill Naruto, only circumstances prevent it each time.

His second telling action is that he heeds Itachi's admonition to turn his anger into hatred. He cuts himself off from the tentative relationships formed with his teammates and tries to harden his heart into that of a cold-blooded avenger. Becoming totally self-absorbed, his need for strength to defeat Itachi becomes an urgent, overbearing lust for power, leading him to leave Konoha to chase the promise of strength at the cost of his soul.

His utter defeat at his brother's hand drives him to seek the quick attainment of strength, in order to regain his standing in Itachi's eyes. He doesn't want to disappoint his brother and is more desperate than ever for his acknowledgment, but at his current rate of improvement it is doubtful if he would ever reach Itachi's level. This makes him all the more resolved to defeat him by any means possible. Killing Naruto would be a rapid way to get his brother's attention, and would conveniently eliminate his rival in Itachi's affections.

Yet, he still wants to be a good person and the good son his father wanted. In his calmer, saner moments Sasuke is glad he didn't kill Naruto, as he doesn't want to become like Itachi and lose his father's respect. He vacillates between doing the right thing by pleasing his father, and giving in to the desire to please Itachi, ultimately becoming wracked with self-loathing and following a path neither would endorse. The essentially unsolvable dilemma haunts him; the need for his brother's affections is too strong to ignore.

This relationship of mutual obsession is as dysfunctional as they come. Both brothers want something the other can't provide: Itachi wants Sasuke to surpass his abilities so he has someone worthy of his esteem, and Sasuke wants Itachi to acknowledge and be proud of him. This can only come about if Sasuke defeats his brother, so Itachi continually hurts him to try to unleash his true talents. However, Sasuke can never fully abandon himself to the hatred Itachi wants, because inside he still craves the attention of his idol -- the man he can't help but forgive.