At least you already got the single. I still haven't gotten it 
I feel ya, yesasia is still looking for my singlev.. WTF that came out 3 days ago~!!
My guess at the hidden meaning of this PV.
Rika and Erika have already been in H!P for awhile (since Erika has been in training for over a year) Yui is brand new and is left out, she really wants to become part of the group. So then shes clinging to rika's leg like please let me be part of the group. But rika and erika are already close, so she has to come in and put on her charm. In the end they realize wow yui you rock(i.e have big boobs) come join our group! The happy end.
Honestly when we think of PV's we think it should have a coherant link to the song that is being sung with it, but alot of japanese PVs arnt like that. They have plots that dont have anything related to the song itself. Like Southern All stars, before they made this video in the 80's that had a nude scene in it, the song had nothign to do with it but they just made a video to kinda look cool. It happened alot for 80's PV's. So i guess its a throw back to that. That and im sure they realize everyone wants rika, EVERYONE, they just wanted trying to get peopel to realize it. Yeah im pretty bored too, whenever i have to study i want to do anything but study.