Is of course... Ayumi! A Ballads took the number 1 spot for April. They don't give exact sales, so we're kinda in the dark. But we can be assured she sold better than anyone else for the month of April (Which folks, tells you right now that A Ballad's sales weren't disappointing in any sense.)

You can find the list here.
http://www.oricon.co.jp/ranking/cd_a...=1&sc=2&term=2