As Zabuza's voice called out the Jutsu, the already natural mist in the surrounding area started to congregate together, the mist spread out fast and far, covering the entire area in its foggy embrace.
Kakashi, Team 7 and Tazuna couldn't see anything, and due to the nature of the Technique, the Sharingan in Kakashi's possession could see that the mist was saturated with Zabuza's Chakra, meaning that even with the Sharingan's ability to see the flow of Chakra in an individual or a limited area around the user, it wouldn't be effective here because everywhere was essentially 'Zabuza' himself...
Kakashi braced himself holding out his Kunai in reverse grip, waiting for his hidden assailant to come, the Genin of Team 7 then formed a triangle formation around Tazuna to keep him safe.
The air was still like water, and the subtle breeze of wind from the sea caused the four Shinobi to be tense due to not knowing if that was just the sea or Zabuza himself was moving towards them. Naruto, Sasuke and Sakura were looking around, trying desperately to get even a glimpse of the Rogue Shinobi but they didn't need to as a voice spoke calmly, echoing behind them:
"… Eyes, Heart, Lungs, Kidneys, Jugular Vein, Subclavian Artery, which one should I choose first?..."
In an instant, Naruto, Sasuke, Sakura, and Tazuna himself felt their hearts stop in their chests, they couldn't move or even speak from the bone chilling coldness Zabuza's voice projected. In the next moment, all they could feel was a rushing wind coming from above them, or move specifically from Tazuna's perspective, the back of his head.
Naruto, Sasuke, and Sakura managed to turn around just in time to see the massive Zabatō coming down towards Tazuna like a streak of cold light, and before they could even react, Kakashi blitzed forward at a speed they have never seen their teacher move before, and in a flash of silver, he was behind Tazuna who was shaking in fear, blocking the massive blade with his Kunai, which if one was paying attention too, can see a faint Wind Current surrounding it, causing it to become much sharper and more durable.
The collision of the two weapons was powerful enough to disperse some of the mist around them, revealing just how close Zabuza was to splitting Tazuna in half. Kakashi then quickly raised his leg and kicked Zabuza in the chest, who twisted mid-air and disappeared back into the mist with absolute silence.
Kakashi with both of his heterochromatic eyes narrowed in a cold seriousness, spoke to his students and client:
"Be careful, Zabuza is known for being a master of Kirigakure's Silent Killing Technique, we won't be able to find him in the mist like this. Naruto, give some light…"
Naruto understood exactly what his Sensei was asking and started going through Hand Seals at a decent pace, but Zabuza seeing this, wasn't going to just let them do whatever they wanted, he had a job to do and rushed towards the blond Uzumaki with the intent of dissecting him.
Dog —> Horse —> Bi-
Just as Naruto was about to finished the last Hand Seal, Zabuza was right in front of him with Kūbikiribōchō coming down on him with the force of a sledgehammer, Naruto nearly panicked and almost fumbled the last Hand Seal but Kakashi came just in time to block the blow, but the force was immense and caused the ground beneath the three of them to cave in slightly and Kakashi's arm's slightly trembling, but Kakashi successfully blocked it, then while still focusing on Zabuza shouted:
"NOW!"
Naruto nodded and formed the Bird Hand Seal and shouted:
"Wind Release: Breakthrough!"
Wind Release: Breakthrough is the D-Rank version of the technique, Wind Release: Great Breakthrough. Kakashi didn't give Naruto the upgraded version due to the fact that Naruto as well as the rest of Team 7 are still new towards Nature Transformation Jutsu and it wouldn't be good to just give them powerful techniques without proper understanding and control of them.
Sasuke was initially against it, but then Kakashi had to explain and demonstrate that just because a Technique has a higher Rank and 'Power' doesn't mean that everyone who learns the techniques would be able to use it to the same or better proficiency as someone who has properly studied and practiced their affinity Techniques properly. So, he started them on D-Rank and some C-Rank Jutsu to help build their understanding and foundations better...
Naruto after calling out the Jutsu took a deep breath of air and then exhaled a great current of air from his mouth into the surrounding area, immediately blowing away all of the Mist in the area, revealing the now exposed landscape to all.
Zabuza growled in displeasure and released all of his 'Killing Intent' onto the group of five. Killing Intent is the manifestation of an individual's bloodlust that is to be projected onto others, however depending on the amount of people the individual has killed and their Chakra Levels, it has varying effects on others.
Zabuza, also known as the Demon of the Blood Mist, and one of the Seven Ninja Swordsman has killed many individuals, especially being a Veteran of the Third Shinobi World War, the amount of corpses Zabuza has buried under his blade is substantial, along with being an Elite Jonin level Shinobi, he has very potent Killing Intent.
Naruto, Sasuke, Sakura, and Tazuna immediately froze up and looks of terror plastered their faces, as in their view, Zabuza instantly morphed into a hideous blue skinned Oni, with blood dripping down from his massive Zanbatō. The surrounding area became dark with the shadows twisting and turning eerily, but that wasn't what they were focused on, instead it was the emergence of the field of corpses that they were suddenly standing on top of...
Naruto, Sakura, and Tazuna have never seen something as horrifying as this in their entire lives, they started trembling all over, their faces pale with fear, and their minds stunned into incomprehensible disfunction. They couldn't move, their breathing was as shallow as the life in the corpses below them, their minds couldn't even start to think properly in response to this evil phenomenon, all they could do was stare at the bloody figure flickering closer to them at speeds their minds couldn't comprehend.
Sasuke was having a far worse time than the three of them, not because of the field or the figure approaching them, but because this is triggering a terrible memory from his past. A dark night that haunted his very mind every night and day… corpses with red and white fan emblems littered a residential area, and right in front of Sasuke wasn't Zabuza, but a shadowy figure covered in streams of blood with the Red Sharingan Eyes of the Uchiha Clan.
These eyes were spinning hypnotically and at a fast rate until they merged together into what could be identified as a curved Shuriken like pattern… then suddenly, the voice of the shadowed figure spoke in a calm and emotionless tone uttering one word:
"Tsukuyomi…" and just as Sasuke's childhood trauma was about to induce a great blow against his psyche, another powerful Killing Intent emerged and brought back Sasuke back from his internal spiralling madness, with the shadows vanishing along with the corpses revealing the original scenario from before.
This new Killing Intent was just as potent as Zabuza's but strangely, it wasn't affecting Sasuke or the other four individuals like Zabuza's was, but instead, like a shield standing proud and protective of them from the enemies aura. Sasuke looked around and found the source of the new Intent was none other than Kakashi himself, holding his Kunai protectively in front of Sasuke and the others, blocking another of Zabuza's blows.
Kakashi exerted force against the Zanbatō and kicked Zabuza in the chest, knocking him back once more and allowing the group to get some breathing room.
Kakashi then turned around and with a bright eye-smile on his scared face spoke:
"Its okay... I will never abandon my comrades…"
Everyone was immediately given strength by the reassurance of Kakashi words and started to relax and get their minds back into focus once more.
On the other hand, Zabuza was getting mad now, he had been kicked twice in the chest and had made a few attempts at the old mans life and nothing was going as planned. It seems Kakashi has earned his reputation as a skilled Shinobi, however, that won't deter Zabuza in the slightest.
Zabuza looked at all of them and started channeling his Chakra again, Kakashi immediately noticed and got back into position, with the Genin and old man bracing themselves for the Rogue Shinobi's assault.
Zabuza formed a familiar hand sign and spoke once more:
"Ninja Art: Hidden Mist Jutsu…"
Then just like the beginning of this battle, the mist in the area proceeded to condense, filling the area once more. Zabuza quickly jumped back into the mist and disappeared from their view.
Naruto seeing this, smirked and spoke
"Seriously, this again.."
Naruto immediately started forming Hand Signs.
Dog —> Hor-
Before he could even form the second Hand Seal, multiple Kunai's pierced through the Mist at extreme speeds, all aiming at different targets. Some targeted Sasuke, Sakura and Tazuna, some even Kakashi, however these where diversions...
Suddenly behind Naruto, a large shadow appeared like a phantom, the figure swung down a large-long shadow that quickly emerged from the fog as a large, sharp blade, closing in on the stunned blond at frightening speeds.
Naruto froze at the sight and with all of his speed and reflexes tried to move out of the way of the Zanbatō's trajectory, but he wasn't fast enough and the blade was closing in on the blond...
Naruto felt dread like none before at this scene, he couldn't move out of the way in time, and from the side Kakashi and the others just deflected the incoming Kunai's and were trying to get to him however they wouldn't be able to make it in time, Naruto's heart started beating faster than it ever did before, with random images and visions from his life til now flashing before his eyes.
From eating his first bowl of Ichiraku Ramen, to the Academy, to his rivalry with Sasuke, meeting their Jonin Sensei, to his dreams of being the Hokage respected by all. All of it flashed in his eyes like a never ending film, over and over again, Naruto felt like crying, but there were no room for tears on this battlefield.
The Kūbikiribōchō was just an a few centimetres away from slicing into Naruto's skull when suddenly Naruto found himself in a completely different position then he was previously. Naruto was disoriented for a moment until he realised that he was next to Sasuke and the others, but Kakashi was now in front of Zabuza where he previously was, with the only thing out of place is the emission of smoke that hovered around the two Jonin.
Kakashi just used the 'Substitution Jutsu' to swap places with Naruto. It is one of the simplest, but most versatile Jutsu that a Shinobi can learn, especially when you are someone of Kakashi's Level and you have learned to perform this Jutsu without Hand Seals and the instinct to use it is engrained into your own Chakra.
Kakashi though didn't have much time to brace himself due to how small of a distance the massive sword was from his face, so he brought his Wind Chakra enhanced Kunai to defend himself.
Both Kunai and Sword clashed together once more like history, however this time, instead of Kakashi being able to successfully block it, he was sent flying back due to not being able to fully brace himself against the immense strength of Zabuza and the massive Zanbatō.
Kakashi was launched back through multiple branches and crashed directly into the lake nearby. However this was what Zabuza wanted, and instantly with Chakra enhanced speed launched himself towards the waterboarded Kakashi, and letting go of his sword for a moment, blitzed through Hand Seal's at an incredible speed.
Ram —> Snake —> Tiger —> Rabbit —> Snake —> Dragon —> Rabbit —> Bird
After completing the Hand Seals, he intoned:
"Water Release: Water Prison Jutsu!"
Zabuza slammed his hands into the water and channeled his Chakra into it, the water writhed at his intent, and Kakashi who was starting to get his senses back immediately noticed the oddity of what was going on, but before he could move all of the water surrounding him rushed and encapsulated him in a massive sphere of highly condensed water.
The Seven Ninja Swordsman of Kirigakure where all highly specialised in Water Release Jutsu, so Zabuza's efficiency with using the technique was even more pronounced than a vast majority of Shinobi around the Elemental Nations.
The Water Prison Jutsu also was designed so that Shinobi trapped inside wouldn't be able to manipulate their own Chakra farther than the distance of the Water Prison surrounding them, this was made with the intent to stop Shinobi from using the 'Substitution Jutsu' mainly during the Warring States Period. However there is one weakness and that is if someone of similar or higher strength is also a master of Water Release of similar or higher skill, then they would be able to manipulate their surrounding water and have a chance of escaping the Prison.
Unfortunately, Kakashi isn't a master of Water Release to begin with, he has copied over 1000 Jutsu across the Elemental Nations, however there are only about a dozen or so that he has truely mastered, and the 'Water Prison Jutsu' wasn't one of them.
Back to the Fight.
Zabuza after successfully capturing Kakashi, let a smirk emerge through the bandages covering his face, and spoke:
"Now… its time to deal with the filth…"
As he said that, he took one hand out of the Water Prison, making another Half-Ram seal and intoned while still concentrating on keeping Kakashi contained:
"Water Release: Water Clone Jutsu"
With that, the water that wasn't being used to keep the Prison up, started writhing, and as if with a mind of its own, shot out of the lake and with a splash on dry ground, started moving up, twisting and turning until it formed the unmistakable image of Zabuza himself.
The Clone then moved and picked up the Kūbikiribōchō, lifting it just as easily as its Original and started walking towards the now terrified group of Genin and civilian. It glared at them with the same cold ferocity as its Original and spoke:
"Its Over…"