Let's start with your writing quality. Maybe my standards are too high, but your sentences are too long (some parts are honestly unnecessary) and some phrases are misplaced. I suggest you read about grammar rules on misplaced modifiers. You should also edit your usage of punctuations, so you can seperate your long sentences better. You're also somehow using some words wrongly.
For example in first chapter:
"Is that anyway to talk to me? I remind you that without me you would be nothing!"
You can rewrite it as:
"Is that how you're supposed to talk to me? Let me remind you, you would be nothing without me!"
There are more errors, but I'll move on to the next.
Story Development. The reason why he died is because he wanted to end the contract. So they blackmail him, then they kill him and the reason is too shallow-- he wanted to end the contract. Since this is under realistic fiction, he will only be blacklisted at most or more blackmail will be used. To make it better, why don't you add more enmity for the main lead. You also didn't mention how he adjusted and stuff.
Character design. It's a bit confusing to read since the personality of other's aren't that distinct. But it's okay. World Background. It's somehow clear. Overall, it's good.
