It's DEF. DIVA's 'Suki Sugite Baka Mitai' performed at the Wonderful Hearts Winter '06 concert. It must've opened the concert or something because it really seems like an opening perf. to me (I, personally, have never seen the concert in its entirety...).
The song is mother-effin' kick-arse (I've been singing it the last few days around school periodically and at home almost constantly), and the way the groups are brought out in backwards chronological order is so cool. :3
First is C-ute in white&pink, newly-formed and not a real group yet.
Then is Berryz Koubou in white&orange. (I really like Yurina's hair when it shows the close-up on her face at :32-:33.)
Followed by W in white&purple.
Biyuuden in white&green. Rika, in the center, looks so pretty, why can't I look like that? D:
Last is Morning Musume in the white&blue.
Cool, yes? I had to go to Dailymotion, though, to find a version that didn't have only Spanish subtitles. When not in AP Spanish 5, I attempt to stay away from any and all Spanish possible.