The story started in a summer day for a 15-year-old Ren, his big sister Rin came home for a vacation for 2 months. And within that 2 months, Rin who only visits her brother Ren every vacation and holidays reunite again to regain their relationship because Ren who acted as a mature one is cold towards his sisters.
It's all nothing but an EroSis!!
Be it his little sister or big sister, but a secret is yet remain untold.