how i can get that scene? can you give me a hint? and the only improvement in the sanctuary is the food?
I (believe) that's an extra to Lucia's story (I'm not sure if it happened before or after the beach threesome). Have you finished the game (Completed all main character's/side stories yet?) You should eventually come across it either way.
Okay yeah! So that scene is the first part of her side story! Just encountered the scene, as she asks you to come down to the hot springs.
It is for a lucy side Story you can still get it if you use the code truestory on the computer.
You can also use your computer. Type "truestory" in the code input area. You can also unlock a Succubus character, Voilet, by typing "spinningtv"