Goblin Slayer (GS) once lived in a small village together with cowgirl. During their childhood they made the promise to go to the city. One day, a relative of cowgirl brought her to the city. It was during this time that the village came under attack by goblins. GS's elder sister made him hide in a cabinet. He was forced to watch as his sister was raped and mutilated by goblins. His whole village was massacred and burnt down in a single night, leaving him the only survivor. Later on in the series, it was revealed that he survived only because he was saved by a Rhea, and it was this Rhea who made him into the GS we know.

GS, together with his party (a priestess, an elf, a dwarf and a lizardman) get inadvertently embroiled in various conflict, despite his desire being only to annihilate goblins. It is during these various fights that we learn that even though GS says he only cares about killing goblins, he actually cares a lot about his companions, and will stop at nothing to save them. (The running joke in the series is that he is socially awkward and lacks common sense at all times, though.)

By the way, the goblins in the series are not dumb. In fact, they can learn the usage of various tools and weapons, and will even imitate human battle tactics, deception etc.

Well that sounds pretty basic..

so other than that the main selling point of the show is just to show a grim and rapey outlook at the D&D fantasy genre and that's about it?

and GS is basically just that? - a serious and monotonous goblin-obsessed dude with no social skills and his growth is starting to have friends he start to care about.

are there anything big happening in the world as an endgame or something like that? will he have to face the ultimate goblin or something other than perpetually go on one goblin-slaughtering fest after another? we've established that dude's a goblin-slaying expert so where do we go from there?

yea i mean you can give a bit of depth to the goblins but in the end they're still basically an infestation going about pillaging and raping villages. not like they have a tendency to organize a military and start invading other kingdoms or become a world-ending threat or anything right?