Since We're in Another World, We Might as Well Give Up

Western fantasy + sword and sorcery + a touch of cosmic horror + play the pig to eat the tiger + heroine included

Note: The story is a slow burn, but things get exciting later.

The protagonist is sent off to save a sword-and-sorcery world.

He thinks that with his abilities, he can thrive there, save the world, and return to modern life to keep slacking off.

But to avoid being rejected by the other world, he has to seal his powers and become an ordinary person first.

Though not entirely ordinary: his special ability lets him grow stronger by devouring things.

He expects his journey through the other world to go smoothly, until he devours an artifact from the Old Ones.