I recommend "Demon's World" to you. It's a fantasy novel about a different world. The story was about an otaku who entered a strange high-level crystal wall system, the Demon World, during his transmigration. This world was covered by the laws of the ancient demons. There were perfect laws, fair law enforcement, and advanced magic technology. The protagonist read a strange ancient book, the Classic of Mountains and Seas, and constantly struggled to improve in this world. I hope this novel can satisfy your male protagonist's fantasy of time travel novels. I hope you like this fairy's recommendation. Muah ~😗