
but is turning your friend into zombie a crime tho? they were already dead I dont understand why everyone is so shock and outrage when dungeon/magic/monster exist in their world?

It was mentioned earlier in the story (chapter 21) during the MC's flashback, but pretty much it's considered taboo and 'against nature.' You are to 'never restore a living organism' because of the moral/ethical issues but mainly because it's impossible to predict the result/form it will take when restored. The MC knew this but tried to 'save/restore' his friends anyway because he had a mental breakdown after watching them get slaughtered (he realized after the impact of his decision but because of his power couldn't fix it). I'm curious how they will try to convict him though because all of his friends should be dead dead now (he had 6 undead friends and the deal was to use the ML's power 1 for each friend plus an extra use (especially one for each dungeon- 7 total)).
Addressing the outrage, if we are being honest, this world is hella unempathetic and hypocritical because they originally criticized the MC for retiring earlier in the story, despite the fact that kid had all of his friends slaughtered in front of him. Then they critiqued him for being the 'weak link' and causing issues and then they praised him and put him on a pedestal.
Ironically the only one who has put any thought into and has been considerate of the MC's situation and mental state is the ML and his main goal was to improve the MC's condition as a means to benefit himself

Brown hair ML is super red flag not even in a good way, apparently he like to lead girls on for "fun" which include MC, and black hair ML has a crazy step?sister that is obsessed with him and think he belong to her, but he himself is a green flag, very kind and endearing to MC. At this point am I even suppose to consider Brown hair as a male lead? since he's the definition of trash.

i'm only on chapter 8 but it seem like everything was kinda handed to him, even the red hair girl feeling for him was too quick and it didn't make any sense, yes he did "train" but that was just running around for a few day and suddenly he's able to defeat 2 person who has been training since probably birth, ig we could say the system help him but it just didn't seem like he earn anything yet.

Not really the system, it's the trait's he gave the character. He needed to reach the proper stamina level to unlock it. The trait gives him the ability to use the swordsmanship the way he wants. He's played the game 27 times, so knowing how to fight from seeing it on the screen you tend to have an idea of how it's done and are able to put it to use when you have the skill to put it to use. The system only allows him to see his growth and reward him for completing quests and such. It doesn't just hand out things because he advanced a point or two.
You don't even know if the body had trained before his possession or not, he might have but we don't know the backstory further. Stamina is very important to do anything really and without knowing what happened prior to his possession we can't say the system helped him in that month he was doing the stamina training. Plus the girl had said she'd seen him swing the sword a few times as well as we saw when he got to the training hall the day he possessed the body he swung it 10 times. He might have gotten a feel of some idea on if the body has some idea of swordsmanship or not at that time and might have practiced some swings after stamina training. We're not sure on what transpired over the month besides his stamina training since they time skipped it after a day or two.
I shoulda let this marinate some more 9 chapter is really not enough
Me too now I’m debating reading the novel