"Though a Flying Thunder God Mark never disappears, there are three situations in which it can no longer be used."
"First, if the object bearing the Flying Thunder God Mark is destroyed. For example, a mark on clothing cannot be rubbed off, but burning the clothing will make the mark disappear."
"Second, if the Flying Thunder God Mark is in a different space from the normal space occupied by the caster. As another form of Space-Time Jutsu, Flying Thunder God cannot be sensed inside certain barriers that isolate space, or within an alternate dimension."
When explaining the second method, Minato deliberately looked at the Nine-Tails and gave an example.
"I once fought the Eight-Tails Jinchuriki and left a Flying Thunder God Mark on one of the Eight-Tails' tails. But once he withdrew the tailed beast's power, I could no longer sense that Flying Thunder God Mark."
"You didn't leave a mark on me too, did you?"
At this, the Nine-Tails questioned Minato suspiciously. After all, this brat left marks everywhere whenever he fought. Had he left one on him back then too?
Perhaps I should find some time to check?
Minato merely answered the Nine-Tails with a gentle, unruffled smile before continuing his explanation to Naruto. "As for the third... the third is only theoretically possible. Flying Thunder God works through a combination of sealing jutsu and ninjutsu, so naturally, it can also be undone using the principles of sealing jutsu.
"But that method is hardly worth the effort. Leaving aside how complex Flying Thunder God's sealing formula is, if your only goal is to disable it, all you need to do upon finding a Flying Thunder God Mark is destroy the object bearing it."
This was Naruto's first systematic explanation of the technique's strengths and counters since learning the