I'm gonna speculate a bit here. I'm not really sure why everyone is hating on the MC. He's clearly the kind of guy who wanted to get isekai'd to a fantasy world because he didn't like living in the world he knew (Modern Day Japan). Worse, he was a convenience store clerk that was looking for another job. For him this is basically just being told "You've lost all your friends, you're homeless, your family is gone, but now you have a host of alternate species and cultures to figure out, you're starting from zero and life still works the same so get to it." That absolutely sucks.
He just got sent from modern day japan to modern day japan with extra work, from a life that already required extra work.
He's trying to find some level of fantasy in a fantasy world because he'd just rather have SOMETHING to make the world feel different to his original one. The fantasy creatures aren't cutting it because they're basically just normal people he could have talked to any day of the week, the only difference being that he's homeless and without a job. The very thing his friend/parent (I assume) was riding him on. Even if it means coming off as rude, he'd rather hold out some hope for actual fantasy, not just a fantasy reskin of his old life. I don't see that as a reason to hate him, dude can be rude all day long, he isn't actively malicious. I think a lot of readers are projecting themselves into his situation and thinking "I'd never do that!" Instead of realizing that he's a completely separate entity with different goals and ideals than them.
Like one guy suggests he just go about telling people he's from a different world and needs help because they see it as the most logical thing....but that's not actually all that logical. You're being way too trusting of strangers in a world you know nothing about, say for how it appears to look like your old world, and basically telling people that you don't know that you're a free pass murder victim (no family, no friends, no connections and no one knows I even exist). That's not something you'd tell people in our world let alone one from a place where the inhabitants have super powers. But sure dump on the MC because...he's being a unique character. OK.