Read Upgrading the Frivolous Emperor Manga:
Stabbed from the start, upgrading with his own wits, self-proclaimed “No.1 Playboy” Wen Zhao Sheng was forced to become the emperor. After being unluckily assassinated, he was reborn miraculously. Now, he plans to use some “dirty tricks” to make a unexpected comeback! This man sure is more cunning than a fox! Playboy emperor x Heartless assassin