You are Sayori, a more-or-less ordinary high school student who is spending her summer vacation helping at an archaeological excavation. One day in the ruins, you happen to notice something shining half-buried in the mud. When you look more closely, you realize it is a pendant, and you pick it up... And thus the story begins.
That night, a girl appears to you in a dream, begging you to save her. She is Hatsuhime, princess of the Mochizuki clan and she was murdered a hundred and fifty years ago. The pendant that you found is the only thing she left behind.
Next morning, you wake up in a place you have never been before - a place that still feels strangely familiar. You are living in Hatsuhime's time, in Hatsuhime's castle, in Hatsuhime's body, and it is your job to save her from her tragic destiny. It seems impossible - until you meet a group of wandering samurais, Yo, Jin and Bo.