Naruto: I start with one door, and I can open it infinitely.

In fact, Lin Chuan couldn't sleep all night at the Root, especially since he was in the same dormitory as Yakushi Kabuto, that traitor, he couldn't sleep at all. He only managed to doze off for a short while in the morning because he couldn't stay awake any longer.

When he heard Kabuto Yakushi getting up and getting dressed, he immediately jumped out of bed, dressed without asking or saying anything, and followed Kabuto Yakushi out of the house to a rather large underground training ground.

With their arrival, four more people arrived at the training ground. In addition to Yamanaka Kaze, whom they had met yesterday, there was Aburame Torune wearing a black eye patch, a boy with short gray hair, and a boy with short black hair. With him and Kabuto, there were six people in total.

"Everyone's here," Danzo said, glancing at the six men, all dressed in Root's black uniform. "Kawa, you'll be in a group with Kabuto; Fu, you'll be in a group with Torune; Shin, you'll be in a group with Sai. From now on, you'll be paired up according to this grouping..."

"Yes, Lord Danzo," the six replied in unison upon hearing this arrangement.

Hearing the voices of the crowd, Danzo was quite satisfied. He then instructed Kabuto, "Kabuto, take them to collect their equipment. You train them for two months. After two months, I have a mission for you..."

"Yes, Lord Danzo," Yakushi Kabuto bowed in response, watching Danzo turn and leave, leaning on his cane. Only then did he smile and turn to the group, calling out, "Come with me, I'll take you to the logistics department to get your equipment. That's all standard equipment for the Anbu; you can't buy it outside..."

The six then went to the logistics department, where they each received appropriate armor, short swords, kunai, and shuriken based on their height and weight, and put them into their ninja tool pouches.

After they were all fully equipped, they returned to the training ground. Kabuto stood in front of them, looking at the five people standing side by side, and called out, "Feng, Tottori, you both have family secret techniques. You can practice them on your own. The main thing is to complement each other's strengths and weaknesses. Only by using your family secret techniques in combination can you achieve a result greater than the sum of its parts..."

"Okay, senior," Yamanaka Fu had already met Tokun this morning, so he took Tokun to another place to train.

"Kawa, Sai, Shin, judging from your three files," Kabuto Yakushi glanced at seven-year-old Lin Chuan after reviewing their information, and subconsciously licked his lips, surprised that this person was a genius.

Although the section on the ninjutsu Lin Chuan had learned was classified, he knew that Lin Chuan was a water-style ninja. He had asked about it casually during their chat yesterday, but he didn't know what water-style ninjutsu the other party knew. So he could only continue, "Sai, Shin, you two should practice kunai throwing first, starting with the most basic ninja tools..."

Then, he looked at Lin Chuan one last time and smiled, "Chuan, come with me..."

"Yes," Lin Chuan replied, silently following behind Kabuto after hearing that it wasn't training but that they were going somewhere with Kabuto.

As they entered the corridor, Kabuto's face broke into another smile, and he said enviously, "Kawa, Lord Danzo values ​​you highly. He asked me to take you to choose a ninjutsu, but you can only choose one..."

"What? Choose a ninjutsu?" Lin Chuan was a little confused. He didn't expect that he would be able to learn a new ninjutsu so soon after joining Root.

He had just learned Shadow Clone Jutsu during summer vacation. If he were to learn a new ninjutsu now, he would have to put aside his practice of other ninjutsu and focus on learning this new one.

Since it's a free new ninjutsu, how could he possibly miss it? He doesn't even know how long he'll have to stay here. What if Sarutobi Takeru takes him out tomorrow? Wouldn't he miss this great opportunity?

As the two arrived at the ninjutsu room, Kabuto Yakushi noticed that Rin Chuan remained silent upon hearing that he could learn ninjutsu, but he didn't think much of it.

After spending a day with Lin Chuan, he figured out Lin Chuan's personality: he was very cautious. It's normal for a newcomer to be cautious.

"You're a Water Release ninja, so you should choose a Water Release ninjutsu. It's probably on the second shelf. You only have half an hour," Kabuto Yakushi kindly reminded him, handing the token to the ANBU guard and standing quietly at the door to wait.

"Okay, senior," Lin Chuan knew his own limitations. He was just a fake genius, not a real one. He wasn't going to choose Flying Thunder God Technique, Impure World Reincarnation, or Spirit Transformation Technique this time...

Choosing these advanced ninjutsu or even forbidden techniques would likely lead to certain death. The only ninjutsu he can choose and learn right now is water-style ninjutsu, thanks to his chakra and decent affinity for water-style ninjutsu.

He could not choose a Water Release ninjutsu that was higher than B-rank difficulty, and the highest he could choose was B-rank ninjutsu. He had already thought it through when he came over. He went straight to the Water Release ninjutsu shelf and looked at the B-rank ninjutsu area on the second floor.

Rank B ninjutsu, Water Release: Water Fang Bullet – A ninjutsu that uses chakra to control water flow and create high-pressure water blades for attack. This technique utilizes the fluidity of water to generate high-speed rotating water jets from any direction to strike targets. When used in conjunction with other ninjutsu in aquatic environments, it has the dual tactical value of disrupting enemy movements and creating opportunities for attack.

B-rank ninjutsu, Water Release: Heaven's Cry—This technique is a no-hand seal, instant-cast ninjutsu developed by the Second Hokage, Tobirama Senju. It is an advanced application of compressed water release. This technique converts chakra into high-density water needles, which are launched from the mouth, and the entire process can be completed without hand seals.

This is the ninjutsu he's looking for. The scroll contains an introduction to this water-style ninjutsu, but as a Naruto fan, he not only knows this, he also knows more about this water-style ninjutsu.

The water needles sprayed by Ame-Cry are about 1 millimeter in diameter and reach a speed of 120 meters per second. They can penetrate regular armor, emphasizing surprise attacks and precise strikes rather than large-scale destruction. They have an A-level penetration, an S-level concealment, an A-level activation speed, and consume only 70% of the chakra of ordinary B-level ninjutsu, making them highly cost-effective.

This technique was used by Tobirama Senju during the Fourth Shinobi World War, penetrating Madara Uchiha's Susanoo, which earned it an A-level rating for penetrating power.

Unless you have the defensive power of Susanoo, being hit by this move is certain death. Moreover, it's a ninjutsu without hand seals, making it perfect for ambushing people. It also only consumes 70% of the chakra of a B-rank ninjutsu, making it ideal for a chakra-starved assassin like him.

He rerolled the scroll and handed it to the ANBU guard at the door for inspection. After confirming that there were no problems, he left the ninjutsu room. The ninjutsu here were all copies, so he could just take them and return the scrolls after he learned them.

Back in the corridor, Kabuto asked curiously, "Kawa, what ninjutsu did you choose...?"

"B-rank ninjutsu, Water Fang Bullet," Lin Chuan lied. It would be a fool to tell the truth to Kabuto Yakushi. Did Kabuto not know that ninja battles are battles of intelligence?

Since Kabuto Yakushi knew that ninjutsu was a ninja's secret, why did he still ask him what ninjutsu he had chosen? Wasn't he trying to gather information about him?

He also knew that Yakushi Kabuto didn't completely believe him, because he had been very cautious since he arrived at Root. It would be strange if Yakushi Kabuto believed such a cautious answer.

"Water Fang Bullet, it works better in water. Do you want to apply for off-site training?" Kabuto Yakushi smiled as he analyzed the ninjutsu for Lin Chuan, seemingly for Lin Chuan's benefit, but only he knew what he was really thinking.

But Lin Chuan could easily see through the old fox's true colors; the fake smile on his face couldn't be more obvious. Nevertheless, he replied, "If I could apply for training outside the training area, I would like to apply..."

"Of course you can apply. Root has more than just this one training ground," Kabuto Yakushi said, leading Lin Chuan back to the underground training ground before reminding him, "If you want to apply for off-site training, you can only go to Root's closed training ground. Just go to the entrance and submit your application..."

"Thank you for the reminder, senior." Lin Chuan was relieved to be able to go out, even though it was a closed training ground. It was much better than staying here. He had his own training methods, but he lacked real combat experience and didn't know if there were any sparring partners in the training ground.

After saying goodbye to Kabuto, and with a meaningful look in Kabuto's eyes, he left the Root underground and asked the gatekeeper for permission to go out to Root's closed training grounds. He then learned that one of Root's closed training grounds was in the Forest of Death.

The place where Naruto and his friends took the Chunin Exams was also a place where large ferocious beasts roamed. After hearing that it was this closed training ground, he turned around and went back to the logistics department to apply for supplies such as ration pills, powder to mask odors, and powder to repel snakes, insects, and rodents.

After making preparations, he applied to go to the Death Forest again. He was quite curious about the place and planned to wander around the outskirts without going too deep. Hopefully, he could encounter some wild boars to practice on and have a taste of meat...

……

In the official setting of "The Book of the Ninja", the Water Release: Heavenly Cry technique is rated as "S-rank for concealment" and "A-rank for activation speed".

Madara Uchiha once pointed out that the threat of the Heavenly Cry lies not only in physical damage, but also in the unpredictability of its attack timing[2].

According to the "Book of Formations", this technique consumes only 70% of the chakra of a normal B-rank ninjutsu, making it highly cost-effective.

This information comes from Baidu Baike (Baidu Encyclopedia)...

……

There is no official separate rating for "penetration".

Its performance in actual combat shows that it possesses strong penetrating power, enough to pierce through Susanoo; for example, Danzo's B-rank Wind Release technique broke through Sasuke's Susanoo.

The overall assessment indicates that its actual effect is equivalent to or higher than that of an A-rank ninjutsu.

Even if this is only A-level penetrating power...