Lucia, the main character, who lives peacefully with her lover Ortho , one day while taking care of the children as a sister. Ortho finally proposes to her, but Lucia can’t forget her childhood friend Nero, who was chosen as a hero about seven years ago. On that day, seven years later, she finally replied to Ortho and wanted to start living a positive life.. Lucia, who followed the figure to the outskirts of the city alone, fainted before she knew it. When she woke up, she found Nero in a strange room who had grown and become a demon king. It is a story about being cuckolded by your childhood friend and having sex because he is obsessed with you now