As far the 12 episodes I've watched yet.. there isn't any proper explanation for body swapping. What's your theory about it?

From recent episodes, from 14 onwards it would be: 

More physical contact that becomes longer as duration over time.

 veneishiag:

I've already watched it till the end. Don't worry, you'll get the proper explanation & theory for the body swapped :D

Oh yess.. I completed it too! 

 Legendary Pink Milk:

I have only seen 10 episodes... I wanted to ask if they body swap another time? I have a theory on why they swapped and that is meteor or something that is going to appear in the sky. They said something like this on the news in earlier episodes. 

Yeah it's gonna happen again. As for the theory you are in right direction but still there's big twist ahead

 Legendary Pink Milk:

Thanks for the reply mate. Much appreciated :))

I am looking forward to them swapping again!!

My pleasure! Enjoy the ride... there's lot of fun ahead ;D