With Kizaru Luffy run out of Haki needed for G5 just like he does constantly with G4 .
With Kaido case Luffy body was giving up, reaching its limit because of all previous damage he took , Luffy literally complained he was already dying before it , and Momo says his voice is fading , voice fading happens when you are about to die not when you run out of Haki.
With Kaido case Luffy body was giving up, reaching its limit because of all previous damage he took , Luffy literally complained he was already dying before it , and Momo says his voice is fading , voice fading happens when you are about to die not when you run out of Haki.