The Grand Duke's Soulmate - Chapter 391: Danger Approaching!

One day, Luo Jian woke up from his sleep and found himself in a locked chamber where the door and window were all sealed. A note with a few lines written on it was tacked to the wall: “Escape from this room within an hour, otherwise, you will die.”

There is a sequel called Reincarnation Night (轮回之夜) that takes place in the same universe but has different main characters

- Description from Novelupdates

Jung Sunwoo was an average man. He had just taken his first job at W&U, a celebrity management company, as a manager. He could finally achieve his dream of being the manager of a world-famous actor or actress. On his way to work, he fell into what appeared to be a lucid dream about his future. As he went on with his day, he realized it may not have simply been a lucid dream.

Li Xiaofei, thrust 500 years into the future, finds himself as a young orphaned man in a harsh, post-apocalyptic world. Raised by a woman only slightly older than himself in the unforgiving slums, he quickly learns that survival requires both strength and cunning.In a world ravaged by alien star beasts, where gangs rule the streets and political factions vie for control, chaos is the order of the day. Amidst this turmoil, Li Xiaofei must carve out his own destiny. Armed with the mysterious Moonlight Treasure Box, he embarks on a perilous journey to make a name for himself and protect the ones he loves.Will Li Xiaofei rise above the chaos to bring peace to his world, or will he be consumed by the darkness that surrounds him?Official BlurbThe star beasts invaded, and Earth’s civilization collapsed. A young man, wielding the artifact Moonlight Treasure Box, drew upon the legacy of three thousand martial arts techniques from various worlds. He protected humanity, won the hearts of beautiful women, slew star beasts, suppressed myriad races, ruled the universe, and commanded the heavens. In the vast cosmos, he was invincible!

I was transmigrated into a webtoon based on an alternate history of a shitty empire.‘I will overthrow this country with my own hands.’And the answer I arrived at upon experiencing it was ‘Coup D’état’.