Seeking the name of a science fiction novel

The story took place 10,000 years later. The world 10,000 years later was just like a primitive society. It relied on the human civilization of the past to survive, and plastic was the currency. At that time, the knowledge chain of humans was interrupted. They only knew the results but did not know the process. The male protagonist was a human 10,000 years later. Every time the male protagonist slept, he could communicate with the female protagonist, a high school student from 10,000 years ago. The female protagonist always taught the male protagonist some strange knowledge in the male protagonist's world. The female protagonist said that she would take the college entrance examination tomorrow and bid farewell to the male protagonist. One time, the teacher was talking about human civilization. It turned out that human civilization was very developed 10,000 years ago, but for some reason, it was cursed by the gods. A huge light appeared in the sky, causing the babies born to be freaks.(I forgot the specific description) The female protagonist happened to be telling the male protagonist about nuclear explosions. The male protagonist felt that this phenomenon was very similar to a nuclear explosion, so he told the teacher about it. I forgot the plot later. In fact, the day the female protagonist took the college entrance examination was the end of the world.