Five years ago, alien beings known as the "Kiseichuu'' invaded the world. With the species endangered, the Kiseichuu are determined to take over Earth through a deadly plan that would gradually wipe out the human race: take away humanity's sexual drive using various methods, letting them die out. In response to the Kiseichuus' scheme, the HxEros device was developed—a powerful weapon that only those with high levels of erotic energy can utilize at its maximum capacity.

Retto Enjou, a high schooler harboring an immense hatred toward the Kiseichuu, joins a group of HxEros users to fight against them and protect humankind. With their gear reliant on erotic energy as a source of power, the team must work together to maintain high levels of libido to ensure their readiness for combat at any given time. Moreover, as he lives in a house full of lustful girls, Enjou should not expect a shortage of power anytime soon.