Explanation

As they spoke, Shiro stood up from beside Kakashi and went over to sit on a rock nearby. Kakashi was still in the middle of his transformation and was not really suited to being moved right now. This was perfect; Shiro could take the chance to explain things to Sakumo.

"Master, you still remember the so-called special rules, right? In the Underworld, you were beside a fire, and you could see what was happening to Kakashi and me in the living world through that fire, correct?"

"That is indeed how it was, but is that very special?"

"Yes. As for the specifics, I can't really explain them clearly, and there are many things I still haven't figured out. For now, what I understand in general is that this really isn't an isolated case. Many people are like that.

"But the reason I call it special is that, because of this, you can only find the corresponding dead through specific people."

Sakumo said, "But as far as I know, behind the fire, there seems to be another world."

"Yes. That is the true Underworld! How should I put it? The place you were staying was only a passage between the world of the living and the World of the Dead. Only those who have truly settled everything in the world of the living can go to the real Underworld.

"And Rin is currently in the passage to the Underworld. She should have still been watching Kakashi before this; I could tell that much. But after that, she disappeared. I'm not very clear on exactly when."

"So that's why you chose to use Impure World Reincarnation?"

"Mm. Her soul can't be allowed to lose control. Perhaps one day, it might become a trump card."

"Sigh... you've worked hard."

As he spoke, Sakumo