Into the New World... With a Gun

"Go in, get the job done, and go home." That's how Gatix prefers his missions, simple and efficient. So it's only natural an eyebrow gets raised when he's told his next mission will take him not somewhere on Earth, but a parallel world untouched by humankind. Figuring it's nothing he and his trusty rifle can't handle, he boldly leaps into the unknown... only to find himself in the middle of a millenial war he has no part in.

But it's not just the Queen of the Demons who's wondering where he came from...

[Isekai - High Fantasy]