Ruka has always dreamed of a silver knight calling her name while she sleeps. Due to her shyness, she has never had a boyfriend in her 17 years of life. One day, a rumor spreads about a stone that could make its owner have a sweet dream while sleeping. Following a strange event, Ruka tries the stone and is brought into the dream. However, what she finds in her dream is not what she expected. She wakes up neither in her bed nor in her world, but in a world where Valkyries rule...