Revenge!
[So the tamed beast part was a lie?]
"I mean I did have a dog as my tamed beast. It just died of old age and is now buried home, however."
[The brother part?]
"I always was a unique child."
[Why the hell did you delve so deep inside that story then?!]
"It was fun seeing your reactions. You were starting to feel sorry for me, right?"
How about I unscrew his head off his shoulder and truly feel sorry for him?
"Haha, let this be a lesson too. Don't trust everything people tell you. I was just joking about it, but someone could exploit that."
Sad to admit but he's right. I know so little about this world that I am easy to trick. An obvious solution is to read, but even then, learning how would take me a long time.
"Don't worry about it. Kidding between friends is something normal."