Introduction to the work: The tomb-keeper family gave Professor Li a key to an ancient tomb with strange specifications, and a mysterious boy said to himself "Let's begin." However, just after Professor Li learned how to open the ancient tomb, his daughter Li Anan received an unnamed express delivery and accidentally obtained another key to the ancient tomb.
After this simple tomb without any mechanism was opened, Li Anan was threatened by the elf girl to take him back to his past life because of tracking the mysterious singing, and was told that there was a so-called bet on fate between them. The gears of fate began to rotate. Li Anan, who returned to the previous life as the current world, suddenly realized that all seemingly unrelated events seemed to be closely related to the elf girl's "bet". Can the unprepared Li Anan not repeat the mistakes of the previous life? Facing the fate of the elf girl, can she win?
(P. S. The plot will have twists and turns, and may be a bit complicated. The previous paragraphs will lay a lot of foreshadowing for the following, and the writing is based on the principle of not writing nonsense.)