Miyako Oguri is a clumsy yet kind-hearted girl who silently carries a torch for Hiroto Tokihara, her classmate who happens to be in a committed relationship with her older sister. Miyako knows that acting on her feelings would never be right, but the sight of them kissing still stings her heart.
One day, a magical key appears in Miyako's shoe locker, giving her the power to go back in time and alter her past. With her heart heavy and her mind racing, Miyako decides that if only she had confessed her love to Hiroto before he met her sister, things might have been different. She travels back two years, determined to rid herself of her unrequited love.
Little does Miyako know that changing the past will only lead to unexpected outcomes. Each tweak she makes affects the future in ways she could never have imagined. Miyako soon realizes that her actions may have dire consequences, and the future she's creating might not be the one she wants.
