Is Oda doing this stuff intentionally? Or did he accidentally make the Ice Oni virus similar to Enma?
1. So Enma draws out Haki whereas the Ice Oni virus draws out Physical strength.
2. Great willpower / Haki can be used to control the Ice Oni rampage similar to how great willpower / Haki can be used to control Enma.
3. In the end, the effects of both Enma and the Ice Oni virus are complete when the person runs out of Willpower/Haki
But then this raises the question, why does Willpower affect both Enma, which is a Haki drain, and the Ice Oni virus, which is a physical strength thing.
Well the answer is that Willpower/Haki is directly affected by how much physical stamina you have.
4. In chapter 935 Luffy says this while wearing seastone cuffs.
We know the only thing seastone does to devil fruit users is “drain stamina” and yet Luffy is lamenting that he can’t use Haki here because of the seastone so it’s very apparent that losing physical stamina directly results in losing Haki.
This is why Willpower/Haki can affect the Ice Oni virus, because Haki utilises physical stamina itself same as the Ice Oni virus.
Lastly, the same way Willpower allowed Hyogoro to retain his mind for a bit even when infected by the virus, stamina is used to keep the virus down completely.
Marco’s flames focus a person’s physical stamina to heal the person and keep the Ice Oni virus from spreading. And since physical stamina and Haki are interchangeable in use, you could say Marco is using a person’s willpower itself to heal the person.
It’s somewhat interesting to wonder what a very strong person would experience getting infected. For example what if Queen infected himself? He would get a huge physical strength boost but would have to sacrifice his Haki to keep himself from losing his mind. This would be a very interesting strategy given he gets a strength boost and can also infect the person he is fighting and after that the person he is fighting also gets a strength boost but has to have the Haki to also keep themselves from rampaging so the two people would become physical monsters with gradually decreasing Haki fighting until one dies or loses their minds.
*Theory by ImmaIvanoM