Mari Tamaki, a second-year high school student who fears she has not been making the most of her youth, contemplates skipping school and going on an impulsive trip, but is too scared to go through with it. One evening, she comes across an envelope dropped by a girl, discovering it contains one million yen. The next day, Mari finds the girl who had dropped the envelope, Shirase Kobuchizawa, who had been saving up the money to travel to Antarctica and find her missing mother, Takako. Taking an interest in Antarctica herself, Mari decides to join Shirase on her journey.