Natsuki, a young woman working for a publishing company, receives an anonymous postcard with a picture of Mt. Everest printed on the back. It reminds her of her brother Kenji, a well-known mountain climber who went missing 2 years ago attempting to climb Everest, who she hasn't seen in 10 years. Why did Kenji ever go to the mountain? What kind of person was he? Natsuki realizes she doesn't know her brother at all, but she believed the postcard to be sent by him, and decides to got to Everest to find the answers to her questions.