Time for some speculation!
0:00 - 0:24
I'm going to say that this is probably a mix between the MC's first visit to the Velvet Room and the actual activation of his Persona. We know from the last trailer there's going to be a train derailing, so this might be where the MC awakens.
0:25 - 0: 35
The sneering, yellow-eyed MC we see is doubtlessly Arsene, unless Shadow Selves are making a comeback. Given the scene immediately following this is probably the first time the MC summons Arsene. From some of the translations floating around, it's probably Arsene who's talking as well. I guess the sticking point for me would be why the MC is already in his thief garb.
EDIT: Just a thought, but from the way the scene transitions, is it possible that the Persona itself creates the costume, like the costume itself is an expression?
EDIT 2: I think I might be looking at this all wrong. Between the golden eyes, the blood, and being consumed by blue flame, we may actually be seeing the MC awakening his Personae to fight two demons. Like, that is him all battered and bloody, and he summons Arsene to fight back, which also creates his costume.
0:36 - 0:53
The only thing worth mentioning here is the scene with the MC getting a mugshot. Maybe it's the opening?
0:55 - 1:02
All of this seems to be taking place on the first day of school. Are the MC, Ryuji and Anne already acquainted?
1:03 - 1:07
I guess they're ditching the hallways for more personalized, interactive dungeons. What could this mean for the schedule?
1:08 - 1:23
So I think this is the real megaton of the trailer. I'm going to go ahead and say that, between the spasms, the heart masks, and straight up having Norn explode from that dude's body, that the enemies we've been seeing are the Persona itself, separated from its host through the process by which people "lose their heart", given a physical form to wander around and then revealing itself to attack. This would also neatly explain how the enemies appear as large knights on the field and become Demons in combat. I still don't have an explanation for the MC's HP and MP, but I think that right there is the first boss/mini-boss of the game.
1:24 - 1:34
I'll break down the next few seconds of rapid screen flashing in order.
First, given how Anne is shocked/scared and Ryuji and the MC are moving in front of her, we might be seeing somebody they know who's been possessed/ "lost their heart".
The people reacting are probably just patrons of the casino seeing the MC jump around. Actually, now that I think about it, given the apparent emphasis on the Seven Deadly Sins, is it unreasonable to assume that this casino would be a Greed dungeon?
The MC leaping onto the Shadow Man and ripping off his mask is probably just an in-game cutscene. Perhaps he's freeing the possessed victim, if that's how that works.
The brief flash of the MC with his face covered in blood is probably from the awakening. The last trailer also ended with the MC's face covered in blood before it vanished when it transformed into Arsene.
Ryuji's going nuts! This might be how people are having their Personae ripped out, if I'm right about the plot.
Lastly, the MC being surrounded by police cars is probably going to be his first public appearance, marking him out as a villain to the general public while he works in secret to save them.
1:35 - 1:38
We see more of the scene with the characters running away from a collapse. Strangest of all is that none of them are wearing their masks.
1:39 - 1:53
Jun, is that you? Chances are that's another party member, or at least some very plot important NPC, spreading the message of the heroes.
1:54 - 2:14
Definitely the MC's first arrival to the Velvet Room, between being shocked that he's there and the build-up to Igor and the Twins. Voice is probably Arsene again.
Here's to some more info in the coming months.
