My mother remarried and I, a high school student, suddenly had a sister. She was gorgeous and beautiful, but she had a prickly personality! I guess she's the complete opposite of me... The moment we met was the worst, but as we lived together, Kokoro gradually softened as I realized she was attractive. She was bright and cute, and contrary to her flashy appearance, she was surprisingly pure... Before I knew it, I had fallen in love with my Hina, Hina. We met as brother and sister, but the natural attraction between us grew and grew and I couldn't stop it.