TLDR: The main characters changes depending on the direction the author wants, regardless of if that's how they would act or not. The main character starts out killing people at the start, but once he has his disciple, whenever he goes to do it, they say no, or get in front somehow and say stop and he does. The main character is again, so strong, that no one can stop him. The strongest human is ant ant to them.
Don't read, tried pushing to chapter 13, can't do any more. This trash wont last long if you want it.
Venting: The Main character was in the demon world for 100 years, a world that is constantly mentioned to be, survival of the fittest. Only the strong survive, sympathy for the weak is a fools errand. During this time, he built the mentality of getting rid of those who appose him in any way, having zero tolerance for anyone doing anything remotely disagreeable such as asking questions. This mindset must surely be deeply embedded in his mind after 100 years. And yet, in the span of several days, he goes from characters being surprised he didn't kill someone for having him wait, to helping innocent citizens because his disciple he has had for a few days doesn't want that.
This is not how it works even remotely.
Take cults for example. People don't lose there belief in there cult leader in the span of a few days, it takes weeks if your not that invested, but in this case, 100 years, so likely years.
Whats something your passionate about? Do you think you could change that belief in a few days? No.
Were not talking about someone hitting you with facts, or whose trained to help you. This is someone saying, please don't do this, please help them, with tears in there eyes.
The point is, he is changing is views so rapidly, that its impossible when considering how long he was in that world for, 100 years.
I get it, you want to see the main character who does bad things to become more compassionate over time. But we are not even past chapter 10 and hes showing drastic changes in his views.
He also has a contract with his disciple so that he can always know what she thinks. This is scrapped 2 chapters later.
Characters who are terrified of him, know that that, and anyone else can not stop him, stand up to him to have him do what they say. This isn't a matter of standards or morals, its idiotic.
You have this character who is stronger than everyone, no one can stop him or hurt him, yet you have people telling him what he can and can not do, even as he had said a few chapters prior that he hates that?
The story is failing to have characters act in a way that they would likely in that situation.