The semi-hero with a demon inside?

Soooo... i was summoned in another world. How cliche...

While me and my friends were coming home from our school in London we suddently found ourselves magically transported to a big room.

The moment I realized what happend i wanted to facepalm myself for my cursed luck, to think this would happend.

perhaps the situation isn't so bad and they're not gonna send me to my death fighting a stupid demon king or something... Right?

But thanks to lady luck, of course the knight goes [Welcome heroes of The Otherworld, this is Arcadia, I am the Royal knight Jacob. We would be thankful if you were to help us deal with a little problem...]

However, I  also heard something cursing... Must be my imagination...

[g- d-e -- h--l -r k-l- --ur--lf... -ha- --e --c-?! w--r- a- i??]