From "The Loneliness of Prime Numbers" or the web drama "Twinkle Twinkle Star".

The 16th episode of the web drama "Twinkle Twinkle Star" is called "The stars and the moon are all lonely prime numbers". In this episode, a boy borrowed a book from a bookstore called "Sea of ??Time and Space". The book was called "The Loneliness of Prime Numbers". The date for borrowing books is May 20, 2021. The book return date is May 21, 2021. On that day, Zhang Wansen learned that Lin Beixing was going to marry Zhan Yu. So, a boy with the same name went to the bookstore and borrowed the book.