The latest version is now 1.23.
You can go to the Succubus House by going left from Outset House (though the house doesn't open up unless you advance the story a little) and then go to the top right corner and talk to the NPC here. This unlocks everything in the Succubus House, though it also locks you inside.
Weird thing is, I've gone through Alpa and Alraune, and still haven't gotten the house to drop. Made it all the way to Harmonia Town and still had nothing result with opening the house. How far off from it opening *am* I? I mean, I have a separate save so I can go through the story itself, but I was hoping to use the house to see what's *different* about the scenes. Would it be too much trouble to just ask for a save if I'm far off from unlocking the house? Or tell me what I'm missing to unlock it?
Seriously, I'm not sure how much further I have to go. Lol