So from what I've understood, they were all reborn except for BQ (dragon), who I'm assuming is immortal. BQ has all the memories, and the drinks he concocts somehow make people remember or simply reminisce about some sort of distant past (their past lives). 

It was genius writing to concoct the final drink by combining the gifts left by their old friends. But what I don't understand is whether the story is set in a modern human age, or were they still in a mystical age? It seems MC has been having weird flashes and seeing fantasy stuff in the very first episode, and the very last scene flashed to a fantasy setting too. But then phones and stuff existed too. 

So was it all some kind of illusion, they weren't actually in the modern world? Or it is a human world, but those with memories (MC and ML) can now see the spirits and mystical elements hidden in a seemingly human world?