In Joo, who had lived a lonely, abandoned life, encounters Jin Do, a bright, warm-hearted man. Jin Do is the first person in her life who takes care of her and gives her love. For the first time in her life, In Joo dreams about being happy for once. But now, In Joo has one last request: she wants Jin Do to let her go, like a summer cold that people have no regrets after suffering.