While watching over her shrine amidst a snowy landscape, Nanami Momozono, the guardian deity of the land, witnesses her loyal companion, the fox spirit Tomoe, fall to the ground due to ominous marks. However, Tomoe's previous master, Lord Mikage, appears after a long absence and saves him by trapping him in a magical pocket mirror. Mikage goes on to reveal Tomoe's past, detailing how he once made a deal with a disgraced deity to transform into a human for the sake of his love for a human. Unfortunately, the curse that came with the deal erased Tomoe's memories of his love and caused his death. In an attempt to suppress the curse, Mikage wipes Tomoe's memory, but Tomoe's growing attraction toward Nanami, his current human master, reignites the curse, leading him toward certain doom. To prevent Tomoe from suffering the same fate again, Nanami embarks on a dangerous journey back in time to revisit the origins of their relationship. Through this process, she comes to understand the depth and intensity of her feelings for Tomoe, which exceed what she had originally thought possible.