Her name is Oniji Feiyi, a judge from another world. In the 21st century, she lives as an ordinary 17-year-old girl.
But now that there are more and more illegal travelers, the Net King's world seems to be about to collapse, and he has to maintain that world. So she set up ten rules for time travel. When she went to that world, she would give each traveler a book - the rules of time travel. If she violates 3 of them, she will be expelled from that world...