Kurumato Umi who has lived as an introverted person with no friends because she grew up with strict parents who worship an evil god. One day, she picks up an unfamiliar polyhedron from an antique shop after a part-time job, and awakens a devilish man (Nyarlathotep). He seems to have come from another world, and he wants us to live in a seaside house as a base to investigate this world! The sea that allowed me to live in the same way as being threatened in the middle. The mysterious shared life of a mysterious outsider and a transcendent shy girl begins!