I think the fact that the ring was on the FOURTH finger of the mystery woman (showing that they are married) was more painful for Ayu...as she dreamt only being his girlfriend..(3rd finger)
and i think...
the PV repeats the scene because one shows the dream and the other shows reality...
the closing eye at the start shows the fantasy...and then opening again with NO ONE in sight (even the guy disappearing)...kinda shows that, in reality, you are really alone..and people around you are strangers...
and THEN,
her friends give her a surprise at the end...
seeming to say,
HOWEVER, despite everything, You have your friends to fall back on
