And if I'm not a huge fan of RPG-s? Or at least those RPG-s where you have to battle with your enemies as if you were playing chess, constantly waiting for the foe to make its counter move?

I'm not very good at explaining but it's not like Fire Emblem if that's what you're wondering.
It's not like Final Fantasy...
I'm not sure what you mean by counter moves.
Maybe it's better to try out the demo first: http://undertale.com/

I tried it out the demo which you linked and played it for around 30 minutes, but it didn't really impress me. I got until the lying ghost after the mouse hole, and all of my HP was gone by that point...

Whoops.

Anyways, I see. At least you tried it, probably poorly taught you how to play. X3

I actually played and finished it yesterday.. i agree it was an absolutely stunning game and the feels at the end were just so intense..i didnt sleep till 5:30am hahah..it was so epic..loved it so much

LOL! Yes, I actually got a friend to play this game.
Oh my god, it hurt to watch because of the mentality of the olden day RPGs! xD
I beat the game like 6 times. >.>; I don't feel special playing Undertale anymore because everyone is playing it now. XD BUT STILL!

Haha 6 times , good effort , yeah it seems to be universally popular.. everyone knows about it..and everyone likes it :P