u/SECTANATOS

I'm going to inevitably get the 2nd one they find the lava rock®

There's clearly some sort of cold war energy to the way information is being withhold from Jodio and the gang. Especially from Meryl Mei since she was the one who sent them to Rohan's house in the first place, saying that the enemy was hiding among the FBI agents does follow a theme I've noticed with Howler. The enemy stand users he hires all had public service jobs like Police, Firefighter, lawyer and investigator (last one might be a stretch to be considered public service). While this secondary mystery antagonist has hired people closer to a federal level and has enough motion to free a murderer convicted with a life sentence.

It wouldn't be crazy to say "oh that has to be the POTUS" but Howler's reaction at being told the president ordered a warrant for his arrest was pure shock. The secrets of making the lava rock are safe guarded by the Howler family for generations to only the firstborn who will get the inheritance, yet Rohan was in posesion of 2 of them at beginning of Jojolands and was in retrospect clearly vigilant of his calls being tapped. This is where the speculation starts but if this secret new manipulative antagonist has Rohan under surveillance it means they've known about him since before the start of Jojolands. Has enough sway in government to use federal agents and hand out presidential pardons/orders. I propose that the secret antagonist is a Brando

Diego Brando was a secondary antagonist 1 part, not nearly as important to the new time line as DIO was in the OG but these new parts still retain some narrative essence of the original counterpart's characters and it seems very likely that a Brando becomes a secondary antagonist of another part. Now they could be the POTUS but narratively speaking this generational need to hide the lava rock's mere existence points towards people that can outlast 8 years in power. Now a Brando in charge a shadowy government organization that can monitor almost anyone across the globe sounds more in line. Either the CIA or Mossad tho I highly doubt Araki would mention Israel but who knows he did start listening to Dua Lippa.

Meryl Mei is still sus af in my book but my XXL Queen is ready to lose limbs for the gang so she good in my book regardless and if a Brando is in this part they're almost certainly going to be related to Jodio's sorry excuse of a father 100%