Perhaps it's related to some sort of new power - up or transformation in the fanfiction. Sometimes in fan - made stories, the author likes to create unique and extreme situations for character development. Naruto might think that by removing his eye, he can unlock a hidden power within him. It could also be due to a misunderstanding. He might be tricked into believing that his eye is the source of some great evil that is about to befall the Hidden Leaf Village and so decides to rip it out to save everyone.
In the fanfiction, it could be that Naruto is in a state of extreme emotional distress. Maybe he has lost many of his friends in a battle and blames himself. He might think that by removing his eye, he can atone for his perceived failures. Also, it could be part of a deal with a dark entity. He may have been forced into this situation where he has to give up his eye in order to protect something or someone else that he values more, like the safety of the entire ninja world.
Perhaps he has been through some sort of mental and emotional breakdown. Maybe he has lost too many battles, seen too many friends die, and he feels that he is a burden or that his death would somehow bring peace to his troubled mind. It could also be related to some prophecy or dark secret he has discovered about himself that makes him think death is the best option for everyone.
One possible reason could be extreme self - sacrifice. Maybe he believes that by stabbing himself, he can save his friends or defeat Voldemort in a very unique way. For example, if there is a dark magic spell that can only be broken by his own life force.
For Sasuke, it could be a huge shock. Since they are rivals and friends, seeing Naruto do something so extreme would make Sasuke question his own role and his relationship with Naruto. He might become more determined to find out what led Naruto to this and seek revenge on those responsible. Sakura would be devastated. She has always cared for Naruto and seeing him harm himself in such a way would make her feel powerless and guilty. She might try to use her medical skills to fix the situation, even if it seems impossible.
One possible reason could be self - sacrifice. Maybe she was in a situation where stabbing herself was the only way to prevent some greater evil from happening. For example, if she was captured by the enemy and they were about to force information out of her that could endanger her comrades or the village.
Well, it could be a dark corruption of power. Maybe in this fanfic, the 'god' power Naruto obtains warps his mind. He might see his family as a threat to his new - found godly status, fearing they'd try to stop him from using his power in certain ways.
One possible reason could be extreme pressure. The Chunin Exams are highly competitive and Naruto might have felt that he was constantly failing and disappointing those who believed in him. Maybe he saw no way out of the situation and in a moment of despair, decided to end his life.
One possible motive could be a misunderstanding. Maybe Haku was disguised as someone else who was about to attack Naruto or his friends, and Naruto reacted in self - defense without realizing it was Haku. Another could be that in this fanfiction, Naruto has been somehow corrupted or influenced by a dark force that made him lose his normal judgment and attack Haku.
It could be that his siblings have made a pact with an extremely evil entity. Naruto, with his sense of justice and loyalty to the greater good, decides that their existence in that state is too dangerous and kills them, though it would be a very difficult and heart - wrenching decision for him.
Another reason could be related to a prophecy. There might be a prophecy that Boruto will bring great destruction in the future, and Naruto, as the Hokage, feels it's his duty to prevent this at all costs. He might think that by killing Boruto, he can change the course of fate and protect the people he loves and the entire ninja world.
One possible consequence could be a change in his fighting style. Without his eye, he might have to rely more on his other senses like hearing and smell, similar to how blind ninja in the Naruto universe adapt. For example, he could focus more on using his chakra to sense the movements of his opponents.