Overall I thought the story was pretty good, but I must say I agree with a lot of your points here.
I would have loved to see more action. I felt like the whole story just dragged along seemingly without end, right until the very end of the book.
My biggest gripe has to be how Yumi came back to life. She gets to come back to life just because she willed it or whatever? Seems pretty weak to me. IMO the story would have ended much better if she had just died, but I guess that would have defeated the romance of the story.