I've tested this on my own PS4 setup from New Zealand, and it's pretty good.
If you want to sing Japanese karaoke at home, and have a PS3 or PS4 console, you can install an app called Joysound.TV, a free download from the Japanese PS Store. You will need to create a Japanese PS Store account first.
Note the app is free to install but needs a subscription (1000 yen for 20 days) to use. You can buy PS Store credits online at places like Play Asia.
Your singing (if you enabled online mode) will be given a score and ranked against other people on the network.