I am looking for about 4 to 5 million yen depending on the legal work that needs to be done. If the transaction is done in Bitcoins I want to make sure that this is reflected in the sales contract and all the official documents so that the legality is clear. As this would be a first this would require some extra work figuring out the legal and tax consequences. Once that is done I would post all the details of this experience on this forum so that other people will be able to emulate this.
I would expect a rent of around 50,000 yen a month. However as this is a resort apartment on the beach it is difficult to get renters for the full year., but during the summer season you might be able to charge a higher rent. This translates to a gross yield of 12 to 15%. Given the maintenance cost of the place of around 18,400 yen a month and annual possession tax of 45,300 yen the net yield is lower at a still hefty 7.5%. As an investment there would be better apartments in Tokyo. But if you enjoy the beach and like a very high speed internet connection, this apartment in Chiba is unbeatable.
The tax on rental income in Japan for non-residents is nearly zero. For details about this and other issues involving real estate in Japan have a look at our Wiki