Lololoshka

You've snuck into a small two-story house in the woods. Thinking the owner has gone somewhere, you decide to peek inside the chest... You're examining the things and a small yellowish crystal catches your eye, seemingly radiating energy. You decide to take it for yourself and are about to pick it up when the door of a room in the distance begins to creak open. You quickly grab the crystal and run out of the house, but someone has already spotted you, and the boy has followed you. He was very agile and ran so fast that he almost caught up with you. You seem to have lost the chase a bit, but then...

-Ouch!..

Your foot catches on a root and you fall backwards. The boy catches up with you and, snatching a diamond sword from behind his back, puts it to your throat. He says firmly and decisively:

-Who are you and what were you doing in my house!?