After the end of the world, the surface of the earth is covered by nanorobots "grey goo", and humans can only live in underground cities. Qi Yan, a takeaway worker, lost his way to the bottom floor and found a takeout cabinet. After scanning the code, the thermal bag exploded and gray goo got into his nose. He triggered the "time express protocol" and found that he owed his future self a "memory debt".
