Kakashi, Shisui, and Kaida just stood there looking at him. After five minutes, Kaida said, "He may actually die like this," and placed a kunai on Danzo's throat.
With a small thrust, he made a small hole and took out all the blood, then used the Healing Palm Jutsu to close the wound. "He is good to go," he said, and then went back to the room.
Kakashi and Shisui both activated their Sharingan. Kakashi just removed his headband to reveal his Sharingan and then started the first round of torture. Danzo first saw a desert, a never-ending desert. He had to keep moving because the sand was so hot that if he stayed in one place, his feet started to melt.
After moving for three days, the most painful part shifted from heat to thirst. He became so thirsty that he even tried to cut his finger off and drink his own blood, but as soon as he cut it, his blood evaporated due to the heat.
After another three days, he was on the verge of dying. Normally, he would have known he was in a genjutsu, but the effect of the poison and the inaccessibility of his own chakra prevented his mind from making any effort to defend him. But he could finally end his suffering and die.
His eyes went open, and he found Kakashi standing in front of him drinking water, the same water he had dreamt of for the last six days. But even though it had been six days for Danzo, in reality, only ten minutes had passed.
But before he could attune his mind to reality, his consciousness once again faded, and he opened his eyes in a jungle, surrounded by many insects. To his dread, he knew every one of those insects; all of them were poisonous but not deadly enough to kill him. The poison was a slow-acting one.
It would slowly melt the bones, muscles, and skin of the area they bit, and Danzo was paralyzed. Once again, an excruciating day of pure torture started.
Once he opened his eyes before his death, he started a cycle of one genjutsu to another. Kakashi and Shisui were competing on who could make it more painful, and Kaida had to give his everything to stop Danzo from getting permanent mental damage.
Even though the basement was soundproof, Danzo's screams were still heard by many members in the Uchiha headquarters. They promised themselves to never get on the bad side of the three people in the basement. Many people who wanted to have revenge against Danzo came to the compound and left with a smile on their face. He was already getting what he deserved.
Most of them were going to stab him many times until he died, but now he would suffer before death. Many people wanted that to happen but didn't have the guts to do so.
But if someone else was doing it for them, then there was no need for them to worry about anything anymore.
In the basement, the mental torture ended after two hours when Kaida finally said that it would be too difficult to keep Danzo sane any longer. Kakashi and Shisui just sighed and shifted to physical torture, removing nails, breaking bones, and even peeling the skin off.
Kaida even thought, 'Maybe I went a little too far in writing those things.'
After another two hours, Danzo was begging to be killed. The cunning and ruthless man was dead long before; now, he was an old man who just wanted his pain to end. He had already forgotten about anything he did in his life.
The only thing going on his mind was to free himself from the pain. He had already tried to beg them to spare his life, but it didn't help, and the pain kept on increasing. He even shifted to requesting his death.
Shisui and Kakashi just looked at him in disgust, but Kaida placed his hand on their shoulders. "The one you guys wanted to take revenge on is already dead. The thing in front of you is just a husk of his previous self. It's time to move on."
Shisui and Kakashi kept on looking at Danzo, who was just lying on the ground, hopefully looking forward to his death and the end of his suffering. "I don't even want to kill him anymore," Shisui said and left the basement. "Same," Kakashi said too.
Now only Kaida and Danzo remained in the basement. "I would have left too, but I know how dangerous you are, and under no circumstances can I let you live. I am sorry, but since I am going to give you a painless death, I want something from you," Kaida said.
"What do you want?" Danzo said with venom in his voice. He knew even though Kakashi and Shisui were the ones who tortured him, it was Kaida because of whom he had suffered. Whenever he thought he had no more strength left in his body and he could finally die, Kaida would heal him and prolong his suffering.
"Oh! You don't have to worry. I will take that myself," Kaida said and placed his hand on Danzo's head. 'I have still not forgotten the vacuum jutsu you used against Sasuke in your last fight. That was the jutsu I liked the most in that fight, something so lethal and invisible and even powerful enough to slice through stones like air. There is no way I would not want that,' Kaida thought.
He started looking through Danzo's memories using his Sharingan. If not for his new power-up of getting a 3-tomoe Sharingan and Danzo still under the effect of the first poison, this would have been almost impossible to do. But now, with everything in the right place, Kaida was able to search Danzo's brain for the training of vacuum release.
There had to be something about it. Even though there were some memories damaged in his mind, the training a ninja did get so deeply embedded in their mind that they could perform those moves in half-sleep, so those memories would be the last thing to leave a ninja's mind.
After some searching, Kaida found those memories and quickly learned everything he could about the jutsu, the training techniques, the uses, its variations, and potential. After doing that, he placed his kunai on a vein in Danzo's neck and sliced it.
Now Danzo would not feel any pain. He would quickly grow unconscious from blood loss and die before he even knew. This was the last mercy he got.
'If I was on Earth, I don't know how I would have reacted after even seeing something like this. Now not only have I seen this, but I was also even helping them. I think all that killing has also killed something inside me since I don't feel any remorse or anything from this.
Heck, I am even relieved that such a big threat is resolved. Is this bad? Should I try to change? No, this mentality is very important for my and my family's survival in this world. There is no place for weaklings here,' Kaida thought.
After steeling his resolve, he went out of the basement, only to find Shisui and Kakashi looking toward the gate. "He is dead," Kaida said. Both of them nodded their heads and disappeared from their positions. Kaida already knew where they went and why they had waited to do so.
Even though they said they didn't want to kill Danzo, they simply couldn't let the man who killed their father be alive. When Kaida waited, they knew he was going to kill Danzo.
As for where they went, of course, to tell their fathers that they could finally move on. 'Luckily, both of their fathers were loyal to Konoha and made sure their sons would remain loyal too. Otherwise, Konoha may have gotten two very strong S-rank ninja as its new enemy. Hiruzen doesn't even know how big of a bullet he just dodged,' Kaida thought and simply went back to his home.
Shisui came back after five hours, his eyes were a little swollen, but the life had come back to them. "Welcome back, brother," Kaida said.