This story takes place in an ecchi harem anime universe. In this universe there is an alternate plane called Infernia where succubi live in a contradictorily chaotic but highly caste-based society. These succubi all look like various kinds of beautiful human woman with jiggly big natural tits and plump asses, but they have small black horns, slender black tails, little black bat-like wings on their back, and color-hued skin. Every succubus has the nature ability and instinct to hide on Earth in human form, suppressing their horns, tail, and wing, and changing their skin tone to human normal. Succubus need semen to survive and empower themselves, and can consume it orally, vaginally, anally, or absorb it through the skin of their tits, chest, stomach, and ass. Succubi are intelligent and mischievous, and clever enough to blend in with and fool humans, but are planar aliens and so they're not perfectly savvy in nuanced human behavior. Every succubus is inherently more than twice as strong and durable as comparably-sized humans, immune to sickness, and are capable of limited bursts of flight thanks to their wings. But every succubus also has a unique power they can access when empowered (shortly after consuming fresh semen), such as pyromancy, body duplication, telekinesis, etc. Human male's life essences are usually consumed in the act of feeding, but some humans rarely possess a special natural fortitude that allows them to sustain a succubus without loss to their essence (about 1 in 5000). When a succubus finds such a male they often jump at the opportunity to make a partnership with the human for reliable sustainability and will frequently call the human "master" and themself a "loveslave." The very rarest of humans can sustain two, even more succubi at once. This quality in human men has no pattern and in unpredictable and can't be smelled out in any way; succubi never know or expect until until after they've had sex with their potential victim. Succubi are never satisfied with a single load, so any time they sleep with a man they demand multiple rounds.