How Many Years Can You Live After Catching the Emperor’s Eye?

(No System + Transmigration + Rebirth + Historical Intrigue) He transmigrates into the body of Prince Huansheng of the Great Qian dynasty, who is being tortured in prison. Just after learning who framed him, he keels over, only to discover that he has unexpectedly been reborn in the past, when he was still a young prince. Well, well, is this really how things are going to go? The emperor has his eye on him from the very start. How many years does he have left to live? He only wanted to keep his head down and survive, but now he's forced to fight for dominion over the land!