Guy sees blood like red stuff on the train and freaks out goes to the same school as the protagonists.
At 4/16 in the red light district a movie theater, vending machine, bar or place that serves alcohol, some sort of place with a flower, and a place with two circular stacks can all be seen
At 4/19, a healing clinic, a shop, a cafe, a recycling place, another movie theater, a basketball court, and a few other places can be seen.
At 4/22, an archery range and statue can be seen
At 4/20 in the school a cafe + a place with a bread icon can be seen. As well as a vending machine
4/18 - Castle dungeon - Ann either joins or has joined already.
5/28 - Art Museum - Yusuke joins and his mentor is related to the dungeon somehow.
8/8 - Pyramid - Unknown girl joins or has joined already. Yusuke is in the party and can be seen running away from the Indiana Jones style trap.
9/28 - Sci-fi Dungeon
The dungeon where they do the all out attack appears to take place in the Pyramid? The Demons/Shadows/Personas are fairly decent level. Stats are noticeably lower than when they're fighting the boss later on tho so maybe it's the castle.
The ball the boss shoots says "Sumiko" on it as well as "Sarve"
The protesters are holding up signs that, according to Mystic, say "Accept your punishment!" and "Face your punishment from God!"