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

A top undercover agent transmigrates into the Great Qian Dynasty and, from the start, kills his twin elder brother in self-defense. With no other choice, he takes his brother's place as county deputy.

He only meant to be a decent official, but then he discovers that his brother had secretly allied himself with bandits.

To keep his brother's good name from being tarnished, he has no choice but to give it his all: wipe out the bandits, solve baffling cases, save the kingdom from collapse, and help his sister-in-law rise to the top.