Transmigrated to the Great Tang, I Keep a Low Profile in the Mountains and Sign In

Jiang Feng transmigrates into the mountains of a Tang Dynasty world and activates a sign-in System. With no idea what the outside world is like, he decides to lie low for a few years. Eventually, a girl named Li Lizhi arrives and disrupts his quiet life. That is when he realizes this is just an ordinary world. Why keep hiding? He is already invincible here. But just as Jiang Feng thinks he will be staying in this world for a long time, the System rewards him with a portal that lets him return to the modern world. Which year he ends up in, however, is up to luck.