#ONEPIECE
"Critical Mass Haki" is going to play a major role.
I think we’ve already seen a tease of this with Garp and Roger, and characters like Shanks have taken it to the next level.
I view it similarly to how Luffy uses Boundman.
He expends a huge amount of Haki to maintain the form for 30 minutes, after which he loses access to his Haki for 10 minutes.
This is similar to what was mentioned regarding Garp and "Critical Mass Haki." Look at it this way: in the fight between Kaido and Luffy, both were using Advanced Conqueror's Haki (Adv CoC) non-stop; Roger also mentioned using it constantly against Xebec.
However, you have to keep in mind that this was just *basic* Adv CoC. What Garp and Roger did against Xebec was different: they poured *all* their Adv CoC into a single attack. The hit was devastating, but they were left with no stamina afterward,just like Luffy after using Gear 4.
That is exactly how I imagine a character like Shanks might have expanded upon "Critical Mass Haki." Instead of dumping his entire CoC reserve into one attack, Shanks focuses his CoC for a specific duration to boost his sword. He employs significantly more CoC than usual, but not the *entire* volume that Garp and Roger used. This allows Shanks to significantly amplify his Attack Potency (AP) through this refined "Critical Mass Haki" form. Much like Luffy uses and focuses his Haki intensely for 30 minutes in Boundman, Shanks focuses his CoC on his sword for a set time without expending it all in a single strike.
This enables Shanks to fight longer with a vastly more powerful weapon, rather than collapsing immediately after a massive attack.
We actually saw a hint of this in *Pirate Warriors* (which, incidentally, also teased Adv CoC). Shanks focuses his Adv CoC onto his sword, enlarging it and significantly boosting both his range and attack potency.
I also think Gaban might use it against Imu (he talked a lot about CoC, so it would be the perfect time to demonstrate it).
I think this could be a good upgrade to the concept of "critical Haki mass",a "next level," so to speak, of using it perfectly in combat.