In the years 2101, Earth becomes very dirty and global warming is very serious, so some people go to space to find new planets where people can live. Min Su is one of the participants.
He always writes letters to his friend Tim.
On the first day, Min Su guides the spaceship's structure, his room and spaceship's sailors. Min Su is very excited. He looks around the spaceship alone. He sees a girl and falls in love with her at first sight. He wants to be on intimate terms, so he approaches first to speak to the girl. The girl's name is Ali. She had been on the spaceship before Min Su.
Min Su writes a letter about Ali, the spaceship and the lifestyle at night. Then he sends a letter to Tim on Earth.
On the second day, Min Su takes the sailors on at tour of the spaceship's structure, his room and the spaceship's command deck. Min Su doesn't think today's schedule is the same as yesterday's. Everyone (who rides in the spaceship) doesn't know it. He saw Ali again, but he doesn't know it. Ali says to him. "You saw me yesterday!" Min Su says "I don't know who you are. Today is my first day in this spaceship." Ali realizes he is deceived on this spaceship. She knows the truth! So she says to him, "Take this letter and hide this letter where only you know." At night, he writes a letter and sends it to Tim.
Third day, Min Su is embarrassed. He realizes today isn't the first day in the spaceship. He asks Ali and she explains to Min Su. He is very surprised as well as the sailors as they are deceived as well with the disappearing memory machine. Ali explains that someone knows the truth.
On earth, Tim gets a letter and he is surprised. because all the letter's dates are the same. He wants to know truth. so he applies to go to find at new planet where people can live.

On the spaceship, Min Su secretly informs truth to the people. All the people know the truth and they want to come back to earth. so they plan to come back to earth.