Edit: Amazon Japan says it releases March 21st
It’s currently listed on HMV for ¥4,180. The email said that it would release April 2nd.
I recommend people wait until it’s on CD Japan or Amazon Japan to buy.
For the previous ones:
BABYMETAL: CDJapan – Amazon Japan
METAL RESISTANCE: CDJapan – Amazon Japan
BABYMETAL Live Selection: CDJapan – Amazon Japan – A!Smart