Zhang Wansen's teenage thoughts over the past 18 years appeare in front of Lin Beixing. When Zhang Wansen was encouraged by Lin Beixing, he fell in love with this free and optimistic little girl. However, when he grew up, Zhang Wansen missed Lin Beixing again and again. He can only be a bystander of the love between Lin Beixing and Zhan Yu. Whenever Lin Beixing was in danger, Zhang Wansen can only guard silently. Lin Beixing looks at the diary, thinking about every opportunity to go to another world, and every time she woke up and realizes that the switch to open the trip was Zhang Wansen's regrettable moments, and the key to the end was not Zhang Wansen's death, but It's the "I love you" they say to each other.