I am a CA final year student and can answer your questions. First of all you are not the service provider even if you buy or sell anything. You are just a seller selling your asset( lets say your car ever heard gst on it?). No matter what the amount of your car is you are not providing any service nor are you making any value addition.
The only person liable to pay GST here would be the japanese exchange. But as they do not lie in the Indian borders they are not taxable too. Moreover what you are doing is import of service and not export of service. The only service provider here is the japanese exchange platform which charge a fee and they would surely be paying an indirect tax to their govt as per laws.
I hope it answers all your queries.
Thanks a LOT. But, this only explains the Case 2. Could u please provide your view on Case 1 as well?
1. Bitcoin sold directly to another person within India against NEFT/IMPS on LocalBitcoins.com. Please note that, it may be considered as inter-state supply as well as eCommerce.
I already said that selling your personal commodity even inter state does counts as a service. For example even if you sell your old car to someone in other state through quickr and took payment throught NEFT/IMPS. This is not a service. Now put your bitcoins in place of car and localbitcoins in place of quickr. Only gst you will be paying here is on NEFT fees and thats it.