I know, the NPCs have finally appeared. I guess I didn't take all the rewards and the game bugged. Thank you, everyone!The building has 3 levels : On top level you find Ashley, Elena and the piano.
Middle level is where you start, with Maya, Josy, the bath, Riona, Tybalt's room.
Downstairs is the party and there you find Lily, Camila, Derek and the champagne. The stairs down are next to Tybalt's room.