@fana:
What's hard to get ? He's more rubbery and can give rubber properties to what he touches. That seems pretty straightforward to me.
Having a rubber body was what allowed him to take a lot of hit. More rubber properties extends the damage he can take. He still feels the pain and it's not like he doesn't have to guard with haki as shown in this chapter.
He could handle the blast breaths fine before Gear 5. No changes here besides the cartoony look.
He can give rubber properties to even people. That's the only unexpected part of his inevitable awakening. That's the part I wonder if it's only possible for his DF.
His stamina isn't exactly infinite or he wouldn't have ran out of Gear 5 once. But if we talk about infinite stamina what about Kaido ? He barely looks like he fought before.
Some of these statements about whether Kaido or Luffy are really being affected by the damage of the fight don't make sense to me because One Piece doesn't often do much to show an opponent getting worn down, besides panting and blood and dirt all over them in not-totally-consistent cross hatching. (Though Luffy dropping Gear Five for a moment is definitely a good example of Oda hinting at a limit, the noted thinning of Kaido's flame clouds in I-can't-remember-what-chapter is another little sign of a fighter's mortality outside the battle itself)
But when you look back at how Oda typically does these things, Katakuri was flipping and dodging through Luffy's attacks at full power, defending with haki and delivering punishing blows right up to the moment he couldn't anymore. His side wound was consistently drawn but never depicted limiting his movement or preventing him from pulling off an attack.
Doflamingo, even being one hit from defeat after the first Gear Four salvo had the strength to wipe out dozens of gladiators, play around with Violet and Rebecca, keep the birdcage up, use his awakening over a wide area, and brought up arguably his largest and most impressive-looking attack of the fight to challenge the King Kong Gun. Then Luffy used his last move and it was over.
Both Luffy and Lucci were confident Lucci had the strength left to take on the entire rest of the Straw Hat Crew, even when he was only one Jet Gattling from falling.
We can keep doing this basically all the way back to Arlong snapping his nose back in place two or three times before it he goes down and it stays broke.
I think Oda maybe skewed the perception of the fight by not really letting the blood and dirt on Kaido's face carry over between forms (particularly to the dragon form) and resetting a lot of Luffy's visual scuffing up with the Gear Five transformation, but I'm assuming that this battle is working the same way as every other one, with the damage accumulating on their invisible health bars until someone becomes unable to fight - and with both fighters able to use their best moves regardless of exhaustion levels until that HP runout happens.
And definitely believe that all the Scabbard and Supernova fights still count against Kaido's invisible health bar as well - he didn't get a full restore just from a five minute breather between each round, he just has that much stamina.