I thought this series was incredible. It just seemed so well put together with little filler. In hindsight every piece played a role in developing the characters and moving the plot forward.
The main character Kazumi is definitely one of my favorites though I have a soft spot for Ayano's character which really resonated with me for some reason. It was fun to see the deep characters and watch them grow and ultimately help each other.
In this respect I actually kind of disagree with you guys. I think the series ended satisfactorily. Sure we don't get to see Ayano and Kazumi get together or anything but it is implied and Kazuma's backstory is revealed completely. Honestly it ended pretty good. I'd rather leave it alone then have another writer take over.