@Edgekin
I'm from the novel, didn't even notice there's anime and manga for this story.
there are gods in earth but the explanation comes later, at least in the novel it did.
But some of it went like this, Earth don't use mana (all of the creature in earth didn't evolve to use it somehow) but the gods of both world will have a small meeting later to converse about god of earth weird activities.
Why are you being edgy anyway, its the start, the whole story is just about a man with an injustice life getting rewarded by wholesome gods while they try resolve the problem with god of earth really abusive attitude toward the mc.
Its supposed to be a slow story so its really awkward when they rush to explain what happening in a few hundreds?(i think) words scene into the first chapter of a manga.
Novels are not easy to simplify into manga.
God of Earth kinda didn't care about anything that's why they didn't get to communicate and just steal mana from earth via mc transfer.