I'm thinking of the version where the player is entering the mansion and discovers one of the succubus's draining another human, if that one exists???
I think you mean Shiro no Yakata, which is a different game.
Oh do you know where to download it??
The creator's name is Zell23, and you can get the latest demo of Shiro no Yakata on his Fantia.jp page (basically the Japanese version of Patreon.)
