For a thousand years, the Vikings have made quite a name and reputation for themselves as the strongest families with a thirst for violence. Thorfinn, the son of one of the Vikings' greatest warriors, spends his boyhood in a battlefield enhancing his skills in his adventure to redeem his most-desired revenge after his father was murdered.
At the young age of 11, Kotoko Iwanaga was abducted by youkai for two weeks and asked to become their "God of Wisdom," a mediator between the spirit and human worlds, to which the girl quickly agreed but at the cost of her right eye and left leg. Now, six years later, whenever youkai wish for their problems to be solved, they make their way to Kotoko for consultation.
Meanwhile, Kurou Sakuragawa, a 22-year-old university student, has just broken up with his girlfriend after he fled alone when the two encountered a kappa. Seeing this as her chance to become closer with him, Kotoko immediately makes her move, hoping to get married to Kurou one day. However, she quickly realizes there is something more to Kurou. With this knowledge, she asks for his help in solving the various issues presented by the supernatural, all the while wishing her newfound partner will eventually reciprocate her feelings.