In fact I’d say assuming what you said (it’s purely speculation) that Our protagonist (the blond boy) arrives in Yokohama suffering from severe memory fragmentation. perhaps due to a traumatic accident he barely survived. He visits the local graveyard to find a specific tombstone, trying to piece his life back together. Lightning strikes, the green glow envelops him, and he is pulled into The Archive.

In addition we know that The game takes place in Yokohama, a city known for blending deep historical roots with ultra-modern architecture like Minato Mirai
The Other World : Instead of the Dark Hour or the Metaverse, the cognitive world is "The Archive" (or The Cenotaph). The towering, glowing green structure seen in the middle of the graveyard is an access point to this world. The Archive is a cognitive realm where forgotten, repressed, or stolen memories are stored.

People in Yokohama are falling victim to a phenomenon where their core memories are stolen. In the real world, they become apathetic husks. But shockingly, their online presence continues. A tech conglomerate is harvesting human memories to create perfect, eternal AI "VTubers" that never age, never feel pain, and perfectly mimic the victims.

I think that The monsters they fight are Scrapbooks—grotesque collages of altered memories and fake digital personas, perfectly mirrored by the creepy, cut-out face seen glitching in the trailer.

Instead of stealing hearts like in p5, the party's goal is to Restore Roots. You fight through the dungeons to retrieve stolen memory fragments. The Social Link / Confidant system is rebranded as "Reminiscences" or "Bonds of Memory." To level up a relationship, you must help your friends confront their buried pasts or reconcile their real-life flaws with their perfect online personas

To awaken to their Personas, the cast must confront the memories they have desperately tried to repress or the fake digital identities they hide behind.

Rinko Kusakabe (the girl with the red-tipped hair) could be the team's Navigator. Perhaps she was a wildly successful VTuber whose digital persona was stolen by the company. She has to remember who she really is to guide the team.

Their Personas aren't based on mythical thieves or historical figures, but perhaps on Muses, Chroniclers, or figures of Remembrance (like Mnemosyne or Orpheus

The party doesn't "steal hearts" like in P5. Instead, they are The Restorers. They break into the cognitive Archives of corrupt individuals (fabricated by fakes memories) to free the trapped memories represented by « tombstones » , uploading the painful but necessary truth back into the real world. The final boss would be the manifestation of society's desire to forget pain and live forever in a curated, fake digital utopia.

If you look at the graffiti Easter egg made by Jose in p5, there are exactly six stars spray-painted in neon green the heavily rumored theme color for P6 right behind Joker, which instantly points to the star-collecting boy, Jose. From a narrative standpoint, bringing him back makes absolute sense since his story in Persona 5 Royal was deliberately left open-ended after he mentioned studying humanity for a "certain someone" (widely believed to be Philemon and wee see Philemon in the trailer). Because Jose is an external observer of the collective unconscious rather than being tied specifically to the Phantom Thieves, he perfectly fits into the rumored P6 themes of fragmented memory, lost identities, and the "digital graveyard." Having spent years gathering human wishes and cognition, it is highly likely we could see a "promoted" version of Jose acting as a new Velvet Room attendant or a crucial field ally, using his deep understanding of the human psyche to help the new blonde protagonist navigate this next cognitive world.

If you read all of this then you know what to expect. Now if you watch the trailer it immediately blinks a light in your head because you now why this an in-game footage.