The songs are normally not recorded in one take it's done in blocks and then mixed in post production and put together to make the song. I know very few musicians nevermind idol groups who would dare record all in one take lol. And i think i remember Tsunku likes to have the lines recorded by everyone so then he has plenty of options so that's a lot to play with post production wise.
Single promo on the front page of CDJapan's website. (Someone was waiting for it; they call her "Sato Yuki" instead of Masaki.) http://www.cdjapan.co.jp/