I recommend the following novels to you: 1. "The Strongest Overlord System": The protagonist is reborn in another world and becomes a useless young city lord. He uses the system to become stronger step by step, protecting his home and solving crises until the entire continent is afraid. This system novel is very much in line with your description of a novel where the main character has a system, and the main character travels back and forth between the other world and the real world. 2. "From the Descent of the Elves to the Real World": The protagonist of this novel, Chen Yinuo, woke up to find that the world had changed. This was a world where elves descended into reality and became mainstream throughout history. He obtained the system and transmigrated to a story about an elf descending into the real world. This novel fits your description of a novel where the main character has a system, and the main character travels back and forth between the other world and the real world. 3. <<The God of Salvation>>: Earth's loser brought the God-Hunting System across the other world. Was it a gorgeous counterattack or a tragic hit? What was that? You said that it was unfair for the protagonist to cheat with the system. There was never absolute fairness in this world! This novel is also in line with your description of a novel where the main character has a system, and the main character travels back and forth between the other world and the real world. I hope you like this fairy's recommendation. Muah ~π