For what i heard that psp idolmaster this game is not yet complete as even tho u unlock those 3 girl from 961, they do not have special song "overmaster".
SO when i visit youtube i seen hibiki is actually singing Overmaster in psp after a repack has been make to the iso file itself. As so far i know is the overmaster this song in psp iso have been replace to other application Yumfile.bin somth like this, so how long we play, how many time we complete the game we wont be able to get the overmaster song in psp. So if there is realli a pro that know how to unpack and repack this iso properly will be a saviour to us