Yuu Hasunuma has never had a stable home after the death of his parents. Since most of his relatives have been vocally opposed to taking him in, Yuu is used to moving from one family to another until he starts living with his mother's cousin. While he does not treat Yuu as a hassle, his uncle has one inarguable condition: Yuu must stay away from the storehouse.

However, Yuu cannot avoid going inside the storehouse any longer when his uncle ends up in the hospital. What he finds there both frightens him and fills him with awe. A voluptuous woman with horns and hooves towers over him, promising to fulfill Yuu's wish in exchange for what he holds dearest. Never having known true filial affection, Yuu wishes for a family—but what he gets far exceeds his expectations. His deal with a demon might just land him in serious trouble!