Training

He returned to Zabuza after wiping his tears.

"Zabuza-sama. I killed him".

"Describe how you kill him. Any problem?'.

"He is still asleep the moment I strike. He's only awake when he's already dead".

Zabuza nods. His tool is growing fine. This is how you kill someone silently. Not letting them fight back is the right call.

Zabuza noticed the blood splattered on his cheek. And also noticed Shou eyes. He cried huh. Then he figured his hand is still holding a bloodied kunai, visibly shaking.

Zabuza knows already that both Shou and Haku are kind. He decides he won't let them kill unnecessarily at that moment in his heart. Although he never voiced such a feeling. He can't admit he actually cared for their feelings.

He used his sleeve to clean Shou's face.

Shou looked at Zabuza who went to pat his head. As if telling him he did a good job.

Feeling him being praised, he feels happy to be recognised for his effort.

"As a Shinobi you have to freeze your heart. You cannot have a heart as a Shinobi. Otherwise it will consume you".

Shao nods. But, for him, he can't be heartless. Even Zabuza can't. But he kept that teaching in mind. For Shou, if he does not feel anything after killing someone he would completely become a non-human… he does want to be that.

Haku congratulates Shou on his first mission.

Although for Shou it's too easy. To a point the supposed ninja died in his sleep. Theres no difference killing him and an ordinary person since all it takes is one surprise strike.

The next day Zabuza takes Haku on a mission aswell. He returned with success. He sees few senbons pierced through the vitals and acupuncture points on the target. The body of the deceased have very little blood on it. A 'clean' kill.

He looks at Haku. He saw the slight shaking, but otherwise, he is in much better condition than Shou. Perhaps its because Haku had already killed many people from his village. But his heart too is kind.

Over time Zabuza trusts their ability to take on missions themselves – mostly C grade mission.

After some time, Shou feels his chakra is enough now, he starts to practice more Ice Release technique alongside Haku.

They had already started training with Ice Release before with the scrolls, especially Demonic Mirroring Ice Technique. But for Shou he lacks chakra and focus on his physical stamina first.

The scroll described the technique in detail as one of the secret techniques of the Yuki Clan. To think Haku discovered it himself from scratch without this scroll shows his monstrous talent.

Shou thinks Haku can be stronger than the original Haku with these scrolls introducing the jutsu earlier.

Or not. Because it's not a matter of strength. It's kindness of his brother that led to his death. He still fears that day would come and practiced hard to prevent it.

They practice one of the common spells that they would most likely use.

Haku and Shou weaved 4 signs, and both of them use the technique of attacking the trees nearby.

Ice Release: Great Frost Breath Technique!

Zabuza watched in amusement seeing the tree frozen.

He notes that Shou frost breath is slightly bigger and that's, abnormal. Because due to his lower age, shouldn't he have lower chakra?

It seems that Shou had bigger chakra relative to his age compared to Haku...

Next Shou and Haku practice the Demonic Mirroring Technique. Shou can make 3 mirrors at most while Haku can make 4. It's because of Shou barely practicing the technique since he focusses more on building his stamina.

Haku and Shou realised they both can enter each other's mirror, which is a neat discovery. Perhaps because they are siblings, or maybe all Yuki clan members can do this?

That seems a bit overpowered… No wonder the Yuki clan eventually had to go into hiding. Who knows how many ninjas went to besiege them out of fear of their power. Think about Uzumaki clan who are in the same situation. People fear the powerful.

When Shou enters the ice mirror, he feels like he's inside a fit small space. And as for the mirror opposite of him, he felt a sense of attraction.

With his will his body moves to the other mirror really fast due to attraction. He can use more chakra to increase the speed. Zabuza has a hard time keeping up with Shou and Haku's movement.

Shou moves again, and this time he injects more and more chakra as he moves. His vision tunnelled more and more at some point he reached the point that he can't even see his surroundings. How does he the attack like this?

Perhaps this is why Haku does not move at his maximum speed. Because it would be difficult to even see; and the momentum from moving at such a high speed would injure oneself if they got counterattacked or, if they directly crashed onto the opponent.

Their body is still fragile after all.

He notes that this is why Haku didn't exactly move at the speed of light. He COULD, but it would endanger him.

Shou thought of solutions. He need Sharingan or something similar to fix his limited vision moving at high speed.

Or…

He just needs to move fast enough he become like the Yellow Flash – speed equals to teleportation.

This means during travel he does not have to worry about enemy attacks because they couldn't attack during flight. And as he appears behind the enemy, he can then attack them by surprise.

As for crashing into opponent, he thought about using ice armament to protect myself. He tried to use ice armament and he could enter the ice mirror space with it. He raised his ice claws, changed it to an ice blade. Haku also sees Shou experimenting and tries covering his body with ice armament.

Using ice armament for the whole body uses a lot of chakras. And to move at greater speed and with greater weight consumes more chakra. The problem is actually efficiency. His chakra would run out after moving between mirrors few times at max speed with ice armament.

Shou decides he would adjust according to opponent level. And that's probably why Haku can be predicted by Sasuke's eye because his speed is against 12 years old genin ninja and don't need to show off.

He suddenly had an epiphany. Wait. Can't I use Rasengan with this?

Thinking about moving between mirrors close to light speed and sending Rasengan to someone sounds overpowered. Literally Minato 2.0.

How can he forget such an important jutsu?? The jutsu is so heavily spammed by Naruto with different colours and variations that Shou felt he's very stupid to not even think about it.

He adds training Rasengan to his list.

He remembers that he needs balloons and rubber balls. Something about spinning chakra in multiple directions, adding power and finally condensing.

And he can also infuse elements into it... Ice Release Rasengan?

Shou felt quite happy thinking about it. He imagined it would freeze his opponent inside out probably. That sounds scary...

Wait. Thinking about Naruto, Naruto uses shadow clones to train. Unfortunately, he doesn't have the chakra to do it. He can only make 1 shadow clone at most now. He tried it and realised its actually more inefficient to train.

If he can make 4 rasengan himself; but him and one clone can only make 3 Rasengan in total, that is so not worth it.

He sighed, thinking about how to use shadow clones to train is only possible for people with monstrous chakra.

He keeps the Rasengan aside first and travels between mirrors seamlessly, stops midway and simulates an attack and re-enter a mirror. Both him and Haku trained hard to master this technique first since it's their best one given the circumstances.

What Shou means is the opponent's level. For below Madara with 5 susanoos tier, Mirror demonic technique is good for even Kages level.

But let say, if Shou and Haku wants to fight Madara or Uchihas with susanoo. There is in fact a jutsu that create ice golem in one of the scrolls. Cold Mother Yuki Onna, creating an ice golem capable of crushing everything on its path and regenerates endlessly. Although, Shou notes that just from the number of seals required and the massive amount of chakra needed he wouldn't be able to use it. And from its property of regenerating, it must use chakra for that. It's similar to Hashirama wood golems.

It's just a pity neither he or Haku has that amount of chakra to use this technique. Damn. Chakra is always the problem to become truly powerful.

He put that aside again and trained.

Over time he realised wind release can reduce air resistance and should increase his maximum speed moving between mirrors.

And after he launched an attack out of the mirror, there's a gap of vulnerability where his opponent can catch him before he could get back into the mirror.

This can be avoided if he launched an attack mid-flight between travel to 2 mirror points. But it's difficult to target vital spots if they are restricted on a single line of sight.

Another method is to use Body Flicker technique back to the Ice Mirror. Shou decides to add the technique to his list since it can eliminate his vulnerability. He also noted that there's also a Wind Release version of Body Flicker that also reduced the air resistance. It consumes more chakra though.

He writes it all down in a note book in case he forgets.

He also decides to make a note on the other page on 'Get chakra!'.

1.Jinchuriki

2.Ryumyaku

3.Moryo

4.Sage mode

5.Light Dragon

Zero Tail

...

He listed all possible things he remembered he could use to get chakra. This lack of chakra limits him... He can't fight Uchiha susanoo, juubi, or Madara or even kaguya without chakra. And at the very least, if they joined ninja war in the future against Madara he does not want to be cannon fodder and die a meaningless death and wants to protect both Haku and Zabuza.

He formed his resolve and will. He makes notes on how to improve.

While writing, Haku went to see what Shou is writing.

"Jinchuriki? What is a dragon vein?". He is confused about what his little brother is writing about.

"Hehe. It's nothing". Shou smiled silly writing all this. Maybe he should get Haku a chakra source as well.

Anyways, Shou talked to Haku to discuss on their understanding of Demonic Mirroring Ice Crystal Technique and shared their ideas and opinions. Haku had the same understanding and went to discuss with Zabuza. Zabuza give some pointers on body flickering technique; while for the limited vision he cannot help on that. He just asks them to only move at such a speed if they are confident.

Zabuza tells them to train body Flicker Technique to an expertise. This technique is done by focusing chakra to the feet and causing an explosion of speed to move a short distance at a very fast speed. If mastered one can even look like he disappeared in an instant due to the sheer speed at max potential.

But it takes practice to control flickering perfectly to align with the mirrors and to do it fast enough.

Shou take the chance to ask Zabuza about techniques to reduce the air resistance during body flicker and while moving in between mirrors.

"It should be common among Wind attribute ninjas. I will try to get the technique". Zabuza said while in thoughts. It should be a common technique among Wind release users... But wind release users are the rarest in the world, and most of them are in Land of the Wind. None of his allies have main Wind attribute.

Or he could try to buy one of the mercenaries and rogue-nin to teach him.

He asks him to keep training first while he thinks about it. He looks at Shou and Haku, who jumps between mirrors at speed even he finds it hard to see.

Even he felt ridiculous that he, an elite Jonin, could barely see them. He is not confident in reacting seeing such speed. He felt as if he was overpowered by 2 kids. He smiled silly thinking about it. The tools he picked are the best indeed. His dream to change the Land of Water will surely be realised with these two.

On other days, Shou and Haku practiced other techniques like taijutsu.

"Attack with all your might. Remember in battle the enemy will try to kill you".

Zabuza drilled combat into both of them without holding back beating their asses, teaching them his skills and shaping them into formidable weapons. Thankfully Haku knows about medical ninjutsu and treated himself and Shou.

"Ouchh… why this ointment so painful…". Its more painful than being cut by a kunai itself. How come??

'It's always like this…'. Haku can only smile at his little brother. He went to use chakra to stimulate his flesh to heal.

Zabuza just watch them two from a distant with cold eyes. Compared to original timeline, Haku show his smiles much more with Shou around.

Shou felt the usefulness of medical ninjutsu and asked Haku to teach him medical ninjutsu but realised it actually involves extensive knowledge and requires dedication.

Shou gives up on that because he does not have the time for it. But he still practiced basics like separating two liquid of different density; useful for poison separation and stimulating flesh to heal with chakra. At least these two can be used directly.

Shou still keeps training daily to expand his chakra field radius so he can sense other chakra fields further. When sensing enemy's chakra, he would need to focus and concentrate to expand his chakra field and to feel inside the field. This however also exposes him to other sensor ninjas as they can feel the opponent chakra field hovering over them as they too trained.

It's a weakness most sensor ninjas deal with.

Shou also trains to hide his chakra presence. Changing its frequency, shrinking his chakra field, and suppressing his chakra flow to avoid detection. However, when doing this he can't use his chakra field to detect others.

Both him and Haku constantly strive to improve to be useful for Zabuza, and to protect each other.