Succubus Research Diary is an upcoming adult visual novel by Arcus Plume. The protagonist of the story is none other than Sarah's mother, Serena!
Follow Serena to the depths of the Underground, where she meets the cute and kindhearted succubus, Nerisha. For one reason or another, the two women soon find themselves having an intimate relationship...
https://store.steampowered.com/app/1495000/Succubus_Research_Diary/