A prophecy foretells of the seal of gods being broken and dooming all of humanity as the king of the underworld awakens… While investigating ancient ruins in the Himalayas, freshman Sera Masao, and his archaeologist parents, find themselves sacrificed by the demons hiding in the ruins. Thus the seal of the gods is broken and the demons can relocate to Earth. The demons, however, require a human host to walk on earth and many demons find such hosts from Masao’s school, Motomichi Private Academy. After forty-nine days since the seal was broken, Masao’s best friend, Midou Akira, and crush, Someya Yuuko are shocked when their friend suddenly appears on school, only suffering from amnesia. Two demons infiltrated in the school, Abe and Arimori Reiko, take interest in the odd event and start suspecting that Masao is a demon as well. They discover that Masao doesn’t contain just any demon, but the most powerful demon lord, Esedes the king of the underworld. However, Akira is disappointed to discover that Masao is yet to give in to Esedes. Yet the demon lord is able to seize control of the body if Masao gives into sexual desire. Thus Masao’s abstinence is the only thing preventing Esedes from raping and murdering everyone.