Traveling Through Liu Bang, Why Did the First Emperor Become an Immortal?

Liu Bang, a high school student from the earth, was originally planning to marry the rich and beautiful Lu Pheasant, then raise an army to overthrow the Qin Dynasty, and finally reach the peak of his life. But one day, he suddenly heard that the First Emperor had become an immortal, and Liu Bang, Han Xin, Xiang Yu... Were all going to be executed. What the hell is this?