The dead man's target - Hyunlix

Book description: Hyunjin has never questioned a contract.
Find the target. Pull the trigger. Walk away.
That's how he survived.
When a new assignment lands on his desk, it seems simple enough: eliminate Officer Felix Lee, a corrupt cop rumored to be deeply involved in the city's criminal underworld.
But the longer Hyunjin watches him, the less the story makes sense.
Felix doesn't act like a criminal. He acts like a man trapped.
As secrets begin to surface and enemies emerge from every shadow, Hyunjin finds himself breaking the one rule that kept him alive for years:
Never get attached to a target.
Because someone wants Felix dead.
And for the first time in his life, Hyunjin is willing to kill to keep someone alive.

Series:
Behind thin walls, on crowded buses, in quiet conversations-danger moves unseen. A neighbor who listens too closely. A student running from a past he can't escape. An assassin who knows too much.
Their stories seem separate. Their lives, unconnected.
But secrets have a way of finding each other.
And when they do, survival is the only thing that matters.