You can tell Asaki's having fun singing the song; at the end, after one last shout of "O-KOOOOOO-MEEEEEEEEE!", he delivers the following spoken line:
"Ahaha...okome oishii!" (Rice is delicious!)
The fact that Asaki and 96 don't appear in the event, presumably due to being Reclusive Artists; instead, they have two stand-ins pose for them. Asaki's in particular is a Caucasian male who looks nothing like him.
"FLOWER" being crossed over into nearly every active BEMANI series, even Miraidagakki FutureTomTom, and even going as far as to be arranged one-to-one just so it could be put into GITADORA.
Any time wac makes a public appearance, he always wears a silly black cat mask.