The person I loved was my sister's fiancée. Our "back side" is revealed... "Non-stop love suspense" full of "secrets" and "betrayals" A good friend's younger sister, Nagisa Miyoshi, and her older sister, Saho Miyoshi. While they were living together, one day, her younger sister, Nagisa, reunited with her first love from high school, Yosuke Asakura, and fell in love again. Nagisa is overjoyed, but when she learns the shocking truth... Yosuke is her sister, Saho's fiancée! ? Why on earth……! ? Being betrayed one after another by those who trusted her, Nagisa is at the mercy of her sister... What will happen to Nagisa and Yousuke's "unforgivable love"? What is the unimaginable “sister Saho's speculation”? The "back faces" hidden by the characters are revealed one after another! "Non-stop love suspense" full of "secrets" and "betrayals" will begin, with shocking developments rushing in like raging waves! "