The OVA was semi-decent... and IMO a disappointment (having played the game...)
A grossly oversimplified summary below:
In my opinion, the ending was much too clean, and Ken got away with just about everything he did...
I wish the producers had stuck with the original ending, where Hotaru finds out, the crash&burn @ the piano concert, and all the other stuff....
call me cruel... but Ken doesn't deserve a good ending either.