How did Guy know he could use the 8th gate if...

[EnigmaticPhenom]

If at 7th gate, you can feel yourself almost dying, wonder how the 8th gate will be, when you concentrate chakra to ur heart and release it all over. After that, the heart becomes so weak it cnt even beat.

 

[MadaraReturns]

how did you know how to breathe

 

[Sir Cool Blizzard]

U don't need to train to open the gates, u just need to know where the chakra gates are.
U don't train to learn how to open the gates (after 1st gate obviously)....u train so that your body can sustain that much of strain. U_U

 

[Xāvî1]

from the experience of the other users! who invented this technique!

 

[KisuneUchiha]

Dai invented it