High schoolers Momoko and Wakaba couldn't be more different—Momoko is flashy and upbeat, while Wakaba stays withdrawn and introverted. Despite their contrasting natures, they are linked by their connection to a single baby.

On a dreary, rainy afternoon, Wakaba abandons her child under a bridge, leaving him there to die. But Momoko soon stumbles upon him, and as she embraces the baby, she feels an intense desire to protect him. As two "mothers," both struggle in their own ways: Wakaba must face her guilt, her manipulative lover, and the blossoming feelings of maternal love that she never experienced herself, and Momoko must learn to balance caring for a young child, school, and her own family.