Hi, I'm new here and a read only member always, but I'd like to let you who are going to come to Japan know this
You can get ROSA of Violet UK or any tunes you want at Japanese iTunes store with iTunes Japanese card.
iTunes card is available at convenience store like seven-eleven in Japan. It cost 1,500 yen, 3,000 yen, 5,000 yen(three kinds).
You can take an account at Japanese iTunes store with it.
You need an japanese address for registration, but it is ok even the hotel address you'll stay.
And of course you can use the iTunes Japanese card after you come back to your country