In the second great ninja war. Konoha saw the rise of three pillars called the Sanins, the students of 3rd Hokage. Even though the name was given by Hanzo who defeated them, Konoha won the war due to sheer manpower, on the other battlefronts, the war ended when the 3rd Raikage and 3rd Mizukage were killed by someone unknown, precisely by an unknown assassin. The victor of the war was Konoha however, this event left the deepest mark in the History of Shinobi world. No one knew how these mysterious assassinations were conducted and who killed the two kages, without anyone noticing. According to the reports the Raikage was killed by a medical ninjutsu taijutsu technique which severed his vocal cords, several bone joints and the brain damaged from the inside. The result was a dead Kage with blood flowing from ears, neck and severed limbs. The Mizukage on the other hand was struck through his heart clean, signs of lightning chakra was found. No one knew who killed either of them, the assassin or assassins who conducted these operations were unknown, nor their affililations were known or their face.
Present Day (After the 3rd Great Ninja war, 2 months after Minato Namikaze's death)
Konoha Year 983
Hiruzen Sarutobi was smoking his pipe and viewing the reports of war on several battlefronts. Konoha had enough manpower to counter all of the Ninja villages alone, it could be said that the amount of ninjas in Konoha nearly equaled all of the villages combined. With such personnel, a win was inevitable and with the feats of Minato Namikaze Konoha won the war with the least casulaties. However, a report in front of him was deeply disturbing him, an Anbu team had sent him medical reports of a dead Mist spy from the Land of blizzards, a small city near Land of Snow. This spy was a double agent for Konoha, his main purpose was to keep in check if Mist advances in the buffer zone, however it was not his death that shocked him, it was how he was killed. The attacker had first attacked his eyes severing them with the use of a very sharpened, pointed blade, possibily this was a ninjutsu previously seen by the third Raikage then his arteries were severed with the use very delicate medical ninjutsu, a chakra scapel. However the reports suggested this was not just any chakra scapel, the severing of the arteries were so brutal that the organs inside were nearly all burnt a possibility of Lightning style. A chakra scapel with the mix of Lightning style, an extremely gruesome technique and the same technique used by the infamous Black Butcher.
Hiruzen then immediately called up on the Anbu captain
Hiruzen: "I want you to assemble best of you personnels and draft a team of ten, go search that area for any signs of a white haired man with a scar on his right eyebrow, if you see him do not engage and retreat as quickly as possible and do not stare in his eyes if he engages in a brawl run as fast as possible or send me the report of his description"
Hearing the orders, the Anbu captain vanished immediately. Hiruzen continued smoking and viewing the report of the dead mist ninja deeply thinking about something. Just then he viewed a pigeon delivering a letter, it was from the guard post 10 Anbu ninjas have left the village for a classified mission. Hiruzen exhaled some smoke and wrapped the files up and called it a day.
(Pov of the Anbu Ninjas)
The captain of this Anbu team was Hizashi Hyuga of the Hyuga Branch family and his team consisted of Kakashi Hatake, Tenzo (a transfer from Foundation), Gekko Hayate,Itachi Uchiha, Rizashi Hyga (a Branch family member), Yūgao Uzuki, Akimichi Nuzuni, Akimichi Toroshi, Aburame Ryoma. This squad consisted of the finest anbu ninjas Konoha had to offer. He had debriefed them the mission, the main task relied on the trackers in the team. However he could not understand who was this guy they were finding and why was he considered such a threat that even with such strong force, he still was not permitted to fight and why could he not recall such a man from the bingo book. Their team immediately commenced their search around the Land of Blizzards after dividing into 2 separate groups. However continuous search of 3 days got them nothing, so he changed his strategy teams of 2 people were created and they were asked to pretend to be tourists and search for their target.
So, the teams were created and one such team was of Kakashi and Itachi.
(Pov Itachi and Kakashi)
Their captain had given them the task of finding a white haired man with height around 6'3 lean built and a scar on his right eyebrow. While such a person should stand out, for the past week no such man was seen. However both of them were patient, the task of ninjas required extreme patience and they knew the importance of such a mission for which such a unique squad was formed. Both of them were dressed as ordinary civilians and after wandering in the area, they soon began to find a place to sit as, in the Land of Blizards every 2 hours a Blizard used to appear. They found a small coffee shop made in an Igloo, short sturdy place that could easily withstand such weather. They entered in the area and were astonished seeing the atmosphere inside. It was warm and had candles in every corner with a scent of some incense sticks, they walked upto a table and saw a boy quietly cleaning some plates near the edge of the bartender table, he had a feminine look on his face however, his hairstyle and way of clothing made it clear he was a boy.
Kakashi: "Hello sir, we would like to have some coffee along with sweet bread with red bean paste."
Haku: "Welcome to our shop, my name is Haku please wait for a minute while I make your order"
Saying it, he quickly began processing the coffee beans and micro wave the bread. Kakashi and Itachi with their ever calculating eyes noticed some scars and bandages on the waiter's hand. Both deduced the same thing that the little boy was training to be a shinobi and the moves he was currently practicing were with Kunai. However both kept quiet and soon their meals arrived.
Haku: "Here is your meal, I hope you enjoy it. In case, you want to reorder or need something else, I will be right here"
Saying this Haku returned to his place and resumed wiping the plates. Itachi and Kakashi ate their meals, left the money and left quietly but a feeling about the waiter named Haku remained in their hearts. After returning they explained everything to their team leader.
Kakashi: "I have a gut feeling, that boy Haku might lead us to our target. This area is full of civilians and no one here practices ninjutsu techniques he could be a nemesis of our target a young lad perhaps his student, sibling or even his son."
Hizashi: "Fine, proceed but be careful I will personally tag alongside you to make sure there are no problems"
The very next morning all three of them tagged along to the coffee shop while their teammates laid around to monitor.