Sister-in-Law, I Really Am My Big Brother

A top undercover agent's soul is transported to the Great Qian. From the start, he kills his twin brother in self-defense, and has no choice but to take his place as county lieutenant.

He'd have been happy just being a good official, but then he discovers his brother was secretly in league with bandits.

To keep his brother's good name from being tarnished, he has no choice but to do everything in his power to wipe out the bandits, solve mysterious cases, save the crumbling state, and help his sister-in-law reach the mountaintop.