Hiruzen asked, "Tell me Fujin, do you know what a vacuum is and its properties?"

Fujin fell into thought, 'Did the academy ever teach about the vacuum? Probably not, though the library might have some information regarding it.'

Fujin answered, "Vacuum basically is a space where nothing exists. Not even air. As for its properties, I don't know for sure. But I have a few guesses."

Hiruzen said, "That's right. Tell me about your guesses."

Fujin replied, "Since nothing exists in a vacuum, the pressure inside the vacuum should be very low, or perhaps non-existent. So if something came close to the vacuum, it would rapidly be sucked inside the vacuum. Though, in that case, the vacuum will no longer be a vacuum."

Hiruzen was impressed by that answer. He nodded, "Very good Fujin. You are right. That is how the vacuum works. The Wind Vacuum jutsus are based on the same principle."

Fujin paid close attention as Hiruzen explained, "Wind Vacuum jutsus are the same as normal Wind jutsus. The only difference is that they have a vacuum core. So, you first have to learn how to create a vacuum core. Observe properly."

Hiruzen extended his arm ahead. Wind formed in his hand, similar to a Wind Explosion jutsu. Fujin observed with all his focus.

A wind sphere formed in Hiruzen's hand. But soon, the winds began moving away from the core. Fujin saw a vacuum sphere forming at the center of the wind sphere. It had a radius of 2 cm.

Hiruzen explained, "To create a vacuum, you just have to remove all air from the space where you decide to create the vacuum."

Fujin nodded. The basic principles were similar to those on earth. Only chakra was used instead of technology.

Hiruzen dispersed the jutsu. Fujin noticed as winds rushed back into the vacuum core. Hiruzen said, "Now you try Fujin."

Fujin extended his hand forward. A wind sphere immediately formed in his hand. He focused on the center of the sphere and tried moving air away from it.

He quickly managed to move the air to one side of the center. However, soon air from other directions entered. Hiruzen observed him carefully.

Fujin struggled for a couple of minutes before making progress. He managed to push the air out from the center in all directions! Slowly, a 1 mm vacuum sphere was formed. Hiruzen noticed. His eyes widened!

Fujin didn't see Hiruzen's expression. His entire focus was on the vacuum core. He kept trying to expand its size. He managed to expand it, but multiple times it collapsed. He kept at it.

Hiruzen watched with shock on his face. He exclaimed in his mind, 'What talent! Danzo needed a week before he could make a stable core. The way Fujin is going, he'll manage to do it today itself!'

After overcoming the shock, Hiruzen analyzed the youth in front of him, 'This kid was talented in the academy, but didn't show any signs of being special. Apart from his higher chakra, all his progress was just a product of dedication. According to Genki, even his higher chakra was a product of hard training.

Even his talent in Wind jutsu wasn't that great. Could he be like those ninjas, whose talent in a particular nature shows at a later stage?'

Hiruzen analyzed more, 'Yeah, there were a lot of ninjas in Kiri and Kumo whose talent in water or lightning elements showed when working on Rank B or higher jutsus. Though the number of similar cases in Fire, Earth or Wind is very low.'

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Hiruzen rated Fujin's talent very high. He expected Fujin to become at least an Elite Jounin. However, he still underestimated Fujin's talent. After his death, Fujin's talent in Wind manipulation would reach a level that the world would label him a calamity!

Fujin was unaware of how much of a shock he had given Hiruzen. His entire focus was on the vacuum core. It needed a very high mastery in chakra control and a very high wind affinity.

A few times he managed to increase the radius of the vacuum sphere to 5 mm before it collapsed. After 10 minutes, he finally managed to create a stable vacuum core of a 1.2 cm radius!

Hiruzen stared in shock! He sighed in relief thinking, 'Luckily I placed him under Renjiro. Otherwise, he wouldn't have become a chunin so early and his talent would have been wasted!'

Indeed, Fujin was lucky. He had intended to spend all 6 years in the academy and build very strong basics so that his survival chance would be much higher. It was only due to the pressure of his other classmates passing, that he decided to pass early so that he wouldn't attract any unwanted suspicions.

If that hadn't been the case, his development would have been stalled by a couple of years. He would have missed the opportunity to gain strength quickly. And would have missed the opportunity to be trained by someone of the same level and dedication as Senju Renjiro.

That would have resulted in him not getting any opportunities to learn the Senju Taijutsu style or Wind Vacuum technique. While he would have eventually learnt those techniques, his progress would have likely been delayed by around 3 to 4 years!

Hiruzen looked at the vacuum core and said, "Very good. Maintain it for 2 minutes."

Fujin didn't reply but followed his instructions. He was able to last 2 whole minutes. Hiruzen was impressed again. He said, "Now encase it with winds and aim it at a tree and try launching it as you do with Wind Explosion jutsu."

Immediately winds began forming around the vacuum core. It took the shape of a sphere. Fujin looked at a tree and threw the Vacuum sphere. However, as soon as the wind sphere left his hand, the vacuum core began collapsing. By the time it traveled 1 meter, the vacuum core collapsed and air entered it. The wind sphere itself collapsed and dispersed.

Fujin was surprised, 'What the heck?'

Hiruzen looked and said, "After creating the vacuum core, you maintained it. However, when you launched it, you couldn't maintain it anymore. That's why air around it entered the vacuum core and your jutsu collapsed."

Fujin analyzed Hiruzen's words and nodded. He asked, "So, how can we maintain it when it is away from us?"

Hiruzen created another wind sphere with a vacuum core and said, "Watch the wind movement around the vacuum core carefully."

He slowly launched the wind sphere towards a boulder. Fujin observed carefully, 'Incredible. The winds are moving in such a way that air doesn't enter the vacuum core! And, there seems to be a thin chakra layer separating the winds and the vacuum core.'

The wind sphere hit the boulder. The winds only caused a few scratches. However, when the vacuum core touched the boulder, the part where it touched turned into soil and was absorbed into the vacuum core. The vacuum core continued for a few inches absorbing everything around it, before disappearing. It left a 6 inch deep and 3 inch wide hole in the boulder!

Hiruzen explained, "In order to maintain the vacuum core, you need to do two things. First, you need to create a thin film of chakra around the vacuum core to ensure that nothing enters it. And then you need to rotate winds around that film in a way that it doesn't damage the thin chakra film and doesn't allow outside air to hit the chakra film either.

When the jutsu hits someone or something, the winds will first damage it and then the vacuum core will hit it. Since the chakra film is thin, it'll break after contact with anything solid or even liquid. As soon as it breaks, the vacuum core will absorb anything it comes in contact with, no matter how tough it is. When it passes through, it'll look like the object is cut into two. But it isn't a simple cut."

Fujin nodded. This technique was very lethal.

Hiruzen continued, "When you cut someone with your sword, only a thin cut forms in their body. As long as that person isn't dead on-spot, a good medic can heal them easily. Even cut arms or legs can be reattached. But with Wind Vacuum jutsus…"

Hiruzen pointed towards the hole in the boulder and continued, "The vacuum core absorbed everything in a 3 inch diameter. Very few medics can heal such a wound. If it hits any organ, such as the stomach or liver, those organs would be ruined on spot. Surviving is almost impossible."

Fujin nodded. Hiruzen's explanation was just as he observed. He thought, 'Damn! Wind Vacuum jutsus will be op! Finally, I'll have a way to hit through the enemy defense.'

He looked at Hiruzen and said, "I understand why you asked me to never use this against a comrade, Lord Hokage."

Hiruzen nodded with a smile. He wanted to teach Fujin how dangerous these jutsus are. He said, "Now that the basic theory has been understood, you will have to try it yourself. Let's begin."

Fujin nodded and began creating another Vacuum sphere with all his attention.