Hiruzen answered, "It has very high demands for learning. To energize the cells and increase their activity, the ninja needs to have at least rank S levels of chakra reserves. In addition, the chakra control has to be extremely high as well. So, it can be done by a very small number of ninjas."
Fujin wasn't concerned by it. Rather, he was pleased. He said, "I satisfy those requirements. What are the risks?"
Hiruzen nodded and said, "Yes, your chakra reserves and control should be sufficient. As for the risks, I will first explain the benefits as the risks are related to it. Energizing every cell in our body is actually very beneficial for us.
If used correctly, it maintains our cells in optimal condition, improving our health considerably. It improves the speed of chakra recovery, the speed at which your injuries heal and reduces the chances of getting sick. It also slows down ageing, but not by much. Ageing is difficult to calculate, but our estimates were around 3-4%.
As for the increase in chakra reserves, it varies. I'm not sure what those factors are because we didn't have enough information since the number of ninjas who met the requirements to try this was very low. Among the ones who tried this method, Danzo had the least gains as his chakra reserves increased by just 12% while Tsunade had the most gains. Her chakra reserves increased by 63%."
Fujin's eyes widened and his face lit up on hearing the benefits. They were very good. He almost became impatient to get those benefits. He thought, 'Damn! 63%? If I get a similar boost, my chakra reserves will be among the highest in the world not counting the Jinchurikis. Even half of that boost will increase it beyond Hiruzen's current chakra reserves. Hehehe, I can't wait. I'm so glad that I brought this up with Hiruzen.'
Hiruzen continued, "As for the risks, they are very simple. You get the benefits I mentioned only when you maintain the cells at an optimal level. If you want more chakra, you can overexert your cells and draw out more chakra, be it in the middle of a battle to recover your chakra or to increase your chakra reserves even further.
If you do that, all the benefits will change into disadvantages. A large amount of cells in your body will begin dying due to overexertion. Though this won't kill you and your body will produce new cells and replace the old cells, it will have grave consequences.
A large number of dead cells will remain in your body. Though our medical ninjas can remove some of them, even our best medical ninjas can't remove all of them. Those dead cells in your body will slowly affect cells around them and slowly those cells will die as well.
Though you won't suffer immediately, it will reverse the benefits you get. Once the number of dead cells in your body surpasses a certain limit, your chakra will regenerate more slowly, your chakra reserves will increase at a slower rate, you will age faster and your body will become vulnerable to diseases as more and more dead cells accumulate in your body.
If you overexert your cells too much, then your chakra reserves could even start dropping, though they will likely still be higher than before you use this technique. You might not feel much immediately, but 15 to 20 years down the line, you'll feel the damage that this will do to your body."
Fujin's excitement died down and he became very serious. Though the benefits were good, the disadvantages were just as bad. He contemplated Hiruzen's words seriously and asked, "If I only maintain the optimal condition, won't it be just beneficial for me? As long as I don't overexert myself, I should only enjoy the benefits, right?"
Hiruzen nodded and said, "You are right. However, that is difficult to do. After all, when you are in the middle of a fight and are heavily disadvantaged, you will be very tempted to do this.
You have fought with Roshi, Kitsuchi, Juzo and Kisame. Against each of them, you could have just retreated easily. Instead, you kept fighting until retreat was the only option.
Once you get this method, you'll be tempted to fight for even longer. Over the years, it will have a detrimental effect on your body. When that happens, you will regret learning this and wasting your potential."
Hiruzen's words surprised Fujin. He thought, 'Ah, now it makes sense why he was so reluctant to tell me anything. Assuming any other method Konoha has, results in an even severe backlash, Hiruzen will be worried that I might injure myself and stop getting stronger in just one major fight.
That said, I never really overexerted myself in any fight. I have only fought within my limits and have always been ready to retreat in case something outside my expectations happens. The only instance when it got very risky was when Roshi suddenly transformed into Son Goku and maintained complete control which I didn't anticipate.
Otherwise, I have always paid more attention to my safety rather than my enemy's demise. After all, what use is it to kill an enemy if I suffer as well? It's not like killing anyone gives me a special benefit or some treasures. At max, I can steal their weapons and money.
Unfortunately, the weapons that are worth stealing are even more rare than a rank S ninja and money is useless in this world for someone who doesn't have to support a huge family, clan or organization. Besides, I can easily steal money from the corrupt Nobles.'
Fujin looked at Hiruzen and said, "You don't need to worry, Grandpa. I will give priority to retreating over overexerting myself in a fight. The only time I will overexert my cells is if my enemy is so strong that I can't retreat safely or if the village desperately needs me to do so."
Fujin immediately cursed in his mind, 'Shit, I almost forgot about saying that I will use it when the village needs me to do so. Luckily, I thought of it in the nick of time!'
Hiruzen was pleased to hear that. He nodded and said, "Good."
A smile appeared on Hiruzen's face. Fujin smiled as well. He thought, 'I have already become a rank S ninja. Though this technique will just increase my chakra and not my combat power, It'll be extremely beneficial for me when my Wind Domain reaches a good enough stage. I'll be able to sustain it much longer and can use attacks that need a lot more chakra with more freedom.
I'm also not sure how much chakra Flying Thunder God will need. Rasenshuriken will also be very pervasive in terms of the chakra needed. So even though my combat strength won't increase immediately, it will give me an amazing base to get stronger much quicker. More importantly, it might also make Ryo allow me to learn Senjutsu!'
Though he generally stayed very calm, Fujin was excited about the number of possibilities that would open up. Unfortunately, Hiruzen didn't say anything and just kept smiling. Not willing to wait any further, Fujin asked, "Grandpa, can you teach me how to increase my cellular activity?"
To Fujin's surprise, Hiruzen shook his head and answered, "I can't."
A frown appeared on Fujin's face. He immediately asked, "Why not? Didn't you say that I have met the requirements to learn this?"
Hiruzen answered, "I did. But I can't teach you how to do it because I am not capable of teaching you that."
Fujin was confused. He asked, "Didn't you say that you helped Orochimaru develop this?"
Hiruzen replied, "I did. Unfortunately, this is too complicated even for me. Even though I helped Orochimaru, I just guided him and helped him avoid some pitfalls that occurred in earlier experiments on increasing chakra reserves. The cellular activity falls under Biology which isn't my strong suit. Doing something that requires you to employ each and every cell of your body is extremely difficult. The only reason why this could be completed is due to Tsunade."
Fujin's eyes widened. He thought, 'Tsunade! That makes sense. Even though Orochimaru is an excellent researcher, his knowledge of the human body is probably far from Tsunade's. But, can Hiruzen really not teach this to me?'
Hiruzen continued, "To be able to increase cellular activity in every cell in your body, you will need Tsunade's assistance. Even I could only do so with her help. Orochimaru was the only one who became capable of doing it without her help. If I try to help you without Tsunade present, I won't be able to handle any unexpected complications that might arise. So, it is very risky and has little to no chance of success."
Fujin fell into deep thought. Ideas clashed in his brain at the speed of light. Unfortunately, he couldn't think of anything. After a couple of minutes, he sighed and muttered, "That sucks."
Hiruzen smiled on seeing Fujin's reaction. For once, he had let Fujin experience the emotional roller coaster that Fujin frequently put Hiruzen and Shikaku through. As he had guessed, Fujin's mood became very down. Hiruzen had dangled something Fujin wanted a lot in front of his eyes and had taken it away without any hope of Fujin getting it anytime soon.
