I like the MC a lot, a lot of people seem to not have noticed the darkness in the MC in the first chapter, but I mean when he's introduced to the church gal and she claims to have magic that can sense lies, he comments on how useful that would be back where he's from, which means at the very least, he lives in a untrusting environment, then when he gets taken to the cave and literally watches a troupe of bandits get slaughtered, most would probably be scarred, but instead he was just kinda unfazed, and then the fact that he knows how to persuade people without beating the ever loving shit out of them, probably leads to a situation where he has to hold a silver tongue. So I have 3 guesses as to his circumstances he came from:
Obviously Japan because that's just how these stories go :
1st: He literally just lives in a strict family, like obscenely strict, maybe involved in politics, and a competitive one at that, a good example is the one in Death Mount Death Parade, the perfect family on the outside but everyone is lonely and hates each other on the inside. That would explain the need for lie detection and why he has such a sweet way with words. But that doesnt work out the whole, I'm cool with seeing murder, type deal.
2nd: He lived impoverished, had to make a living conning, and that's where he got his communication skills. The need for a silver tounge with the threat of loan sharks and police, and also finding out if he's set-up or not(which might be how he arrived, he died in a set up and got send to the fantasy world, which is why lie detection would've been useful.) It would make a lot more sense on why he was better suited for murder, because while still uncommon, it would be more common than if he lived a normal life.
3rd: Super genius intellect Otaku NEET who is antisocial and dropped out of school and stayed in his room. He tripped down the stairs when going to get a glass of water and badda boom badda bing here we are.