Nocturne is my jam. I loved a review that called it something of a isolating, lonely and claustrophobic feeling of a game. And indeed when you are walking around the curved corridors of the kalpas, you feel like you are indeed deep deep below the earth.

Since you’ve played P4, Persona Q might be a good on-ramp into Etrian Odyssey. It’s essentially EO’s gameplay with personas, characters and skills/spells from P3 and P4. Q2 has the P5 characters as well but only the Japanese voices (which is why I never got around to it).