Fujin began practicing. Hiruzen had instructed him to practice with a 1 cm radius vacuum core for now.

After creating the vacuum core, he began encasing it with a thin layer of his chakra. It needed delicate chakra control. However, thanks to his Senju Taijutsu style training, his chakra control was good enough.

After a few failures, he managed to learn it rather quickly. The next challenge was to form winds around it to add another layer. This time he failed a lot more. If the winds hit the chakra film even a bit, it would collapse. But, soon he managed to create a proper Vacuum sphere.

In Fujin's right hand, a wind sphere rotated. At the center of this wind sphere was a thin chakra film that encased a 1 cm radius vacuum core. Hiruzen thought, 'Incredible. He got the basic form right in less than 10 minutes!'

Hiruzen said, "Now throw this sphere at a tree."

Fujin nodded and followed his instruction. The Vacuum sphere travelled for 10 meters when it suddenly began collapsing. Fujin observed closely and muttered, "The winds hit the chakra film and entered the vacuum core."

Hiruzen nodded, "That is the case. You have to ensure that the winds don't hit the chakra film even when it is travelling. And you need to make the chakra film sturdier while not increasing its thickness."

Fujin nodded and began practicing again. For the next 7 hours, Fujin kept experimenting with the wind flow and tried making the chakra film sturdier.

Hiruzen kept watching the whole time. He initially watched Fujin with fondness due to how dedicated and hardworking he was. However, after 7 straight hours, he sighed, 'I expected him to take a break for breakfast and lunch. Instead, he just grabbed a few ration bars and stuffed them into his mouth! He didn't even offer them to me.'

Hiruzen hadn't carried anything to eat. A couple of times, he had even asked Fujin to take a break. However, Fujin replied, "Just some time, Lord Hokage. I think I have got a handle on this!" After replying, he would get lost in practice and not even look at Hiruzen.

He did talk with Hiruzen a few times, but it was regarding issues in the training. After getting the answers, he focused on the training once again.

Finally, he managed to get a hang of it! He created another Vacuum sphere and threw it in the air. It traveled for around 100 meters in the sky before collapsing.

Fujin looked at Hiruzen, who nodded and said, "Good. This is perfect. Now try it on trees or boulders."

Fujin nodded and followed his instruction. He created a vacuum sphere and threw it at a tree. It hit the tree and pierced through it, creating a 2 inch wide hole in the tree.

He smiled and began creating more Vacuum spheres. In the next few minutes, dozens of trees were pierced. However, every Vacuum sphere after piercing the tree would collapse.

Fujin wondered, 'This is definitely good but if it collapses so soon after piercing a tree, it won't be that lethal. Maybe creating a bigger vacuum core might help it go longer'

Hiruzen wasn't aware of Fujin's thoughts. He looked at his performance and praised him, "Great work Fujin. However, let's stop here for today."

Fujin looked at Hiruzen and protested, "But Lord Hokage, I can still train!"

Hiruzen shook his head and said, "Your chakra is almost exhausted. If we train more, then you might not be able to train tomorrow. The next step of training will be just as challenging as today's. So let's stop for today."

Fujin reluctantly nodded. Hiruzen instructed, "Don't practice Wind Vacuum style in my absence. Preferably, don't use any more jutsus today and meditate to recover your chakra quickly. We will meet tomorrow at 7 AM as well."

Fujin nodded and thanked Hiruzen for his help.

Hiruzen smiled and left thinking, 'Finally I can have some food! Didn't expect him to train continuously for so long. His teammates left after a couple of hours of training. Still, to get the basic version of Wind Vacuum style down in a third of a day! Fujin is very talented in Wind Release.'

He chuckled thinking, 'I wonder how Danzo would react when he knows that an 11 year old kid learnt in under 8 hours what he needed 9 days to learn!'

After leaving, Fujin went to the shopping area for ninjas. He entered the same clothing shop as he did almost a year ago. Fujin asked the shopkeeper to make similar clothes for him as the ones he was wearing, but tailored to his current measurements.

The shopkeeper took Fujin's measurements and commented, "You are doing well kid. You've gained 4 inches in less than a year!"

Fujin replied, "Yes, thank you."

The shopkeeper smiled and said, "I saw you in the chunin exams. You were amazing! Congrats on winning the tournament."

Fujin nodded. After taking the measurements, the shopkeeper asked, "I have one product to show you. Most ninjas buy this from me."

Fujin asked, "What product?"

The shopkeeper picked up a box and opened it. He took out something that looked like chainmail armor. Fujin checked it. It felt very sturdy! It would be able to block stray shurikens and kunais as long as they weren't enhanced with chakra flow. It would likely reduce damage from shurikens and kunais thrown directly at him as well. When combined with Chunin Vest and Shirt, it's likely that normal shurikens would find it difficult to hurt him. Of course, the rest of the body will still be vulnerable.

The shopkeeper said, "This is a Mesh Upper Bodysuit. It is"

Fujin cut him and said, "I'd like 2 sets of this as well."

The shopkeeper nodded and said, "Alright, it'll take us around a week to make everything for you. So visit me after a week."

Fujin nodded and left.

The next day, Fujin once again began warming up while waiting for Hiruzen to show up. Hoka, Mieko and Hiruzen all arrived slightly before 7 AM.

The group split up once again, with Hiruzen's main body staying with Fujin.

Hiruzen instructed, "First, let's check what you have learnt so far. Use a couple of Vacuum spheres on that boulder."

Fujin followed his instructions and tossed a couple of Vacuum spheres on the boulder one after another. The first one pierced more than halfway through it, while the second one pierced through it.

Hiruzen said, "Good. What are your thoughts about the Wind Vacuum style?"

Fujin thought for a bit and said, "It is very strong in terms of piercing capability. But, the vacuum core collapses soon after hitting the first target. So even if this technique pierces through any defense, it won't be able to harm the ninja hiding behind those defenses."

He looked at Hiruzen and said, "I wonder if increasing the size of the Vacuum core will resolve this."

Hiruzen replied, "Good analysis. But no. Once the vacuum core begins absorbing, it'll collapse quickly."

Fujin frowned, 'I don't remember too well, but I think Danzo's vacuum jutsus kept traveling even after piercing rocks. Will that not be the case here?'

Hiruzen smiled seeing Fujin analyze with a frown. He said, "But, there is a way around this to make the Wind Vacuum jutsu last much longer and hit multiple targets in its path."

He extended his right arm towards a tree and said, "Watch."

Fujin observed carefully as a Vacuum sphere formed in Hiruzen's palm. His eyebrows furrowed. The Vacuum core was different, but he couldn't understand what exactly was different.

Hiruzen launched the Vacuum sphere. It pierced through the tree, but maintained its form and kept going ahead. Fujin watched with eyes widened as the Vacuum sphere pierced through 13 trees before collapsing! He just exclaimed, "Wow!"

Hiruzen smiled with satisfaction at seeing Fujin's reaction. Fujin asked, "The Vacuum core looked different. What did you do?"

Hiruzen extended his arm ahead and said, "Observe carefully again."

A small Vacuum core slowly began forming in Hiruzen's palm. A 1 cm radius vacuum core was formed. A thin film of chakra then encased it. However, instead of forming winds around it, vacuum began forming around the chakra film!

While this vacuum was being formed, chakra began extending out of the thin chakra film. The vacuum outside the chakra film encased it entirely, but it was divided into 6 equal parts. Between those 6 parts, Chakra flowed. In addition, thin threads of chakra existed even within these 6 vacuum parts. They looked similar to veins.

Hiruzen walked towards a nearby tree while saying, "Follow me and observe what happens when this hits the tree."

Fujin followed him. Hiruzen slowly pressed this vacuum core against the Tree's trunk. The truck began disintegrating and getting absorbed in the vacuum. However, after entering the vacuum, it drifted towards the chakra in between the vacuum. After entering the chakra flow, they were thrown out of the vacuum core.

Fujin was surprised. He said, "The absorbed materials are thrown out. So the vacuum core is maintained. And the central most vacuum core was never even hit."

Hiruzen dispelled the jutsus and nodded, "This way, you can maintain the vacuum core for longer. Once you master this, your enemy will have to dodge your jutsu. As blocking them will be near impossible."

Fujin nodded and grinned, "This looks very lethal! Thank you, Lord Hokage!"

Hiruzen smiled and said, "Now you try creating such a Vacuum core." Fujin nodded and got to work.