... You can't really go so far as to call that plagiarism, when either way it's Naoki's song. If they took Riyu's lyrics without crediting her somehow, then it might be plagiarism, but they changed the words and just took the tune -- which is Naoki's to begin with.
Even if it weren't Naoki's song, people do covers all the time. is new-BeForU plagiarizing Denki Groove with Shangri-La?
The whole thing kinda sucks either way, since I want BeForU to be included. But I understand they probably did it to save money, since Konami is a business after all.
(I am still holding out hope that maybe groups like BeForU will come back into fashion and maybe they'll go back to Konami. ;~; or Noria or Sayaka or one of the solo people. But I recognize that's not terribly likely.)
Yeah, I mean... is Riyu a plagarist if Freedom took 1/6thbillionth's melody? :p Or heck, is she a plagarist because of her begin album - all the songs on there do take the melody from another song that has already existed.