Haruka, a succubus from the demon world, came to the human world with one goal. To kiss tons of cute human girls and suck their vital energy! However she's had no luck with that and ends up collapsing in the street, only to be found by sisters Yuuna and Sana. She immediately latches onto them and ends up as a freeloader living in their home. Haruka is more than happy being in this predicament, but everything changes when Sana, the younger of the two sisters, confesses to her.