"I really like you, big sister." Having lived with her heart locked away, believing that no one would love her and that no one would hold her, the plain girl Sayuri has always been cautious. After 13 years, her younger sister Mikoto unexpectedly returns as an angel! While her heart races at the sight of her cute sister, there are moments when she feels a twinge of envy. Will living with Mikoto add more love to Sayuri's heart?! Her younger sister's intense love feels heavy...!