Kaede and Yuzu not getting together was supremely disappointing. They had great chemistry. I wish they had been the leads.
Ending it on a Rei Ayanami "What is this human emotion you call love?" sort of revelation was the worst possible copout, and they dived into it head-first. The ending basically states "We've been best friends since we were little, have intense makeout sessions twice an episode, spend all our time together and go to great lengths to protect our relationship, but
do we love eachother?" There's a moment in the final episode where it seems like Haruka is going to turn on Yuu and date Mitsuki, and the resolution is that Haruka literally doesn't understand the definition of romantic love so she didn't even know what that meant. Ech.
The ending had a lot of tone conflicts as well, where they still throw up the visual gags and kooky music as the conflict of the series is being resolved in a pretty heavy (relative to the series) scene.
Arguably, Mitsuki's the protagonist. At first she disapproves of Yuu's and Haruka's relationship, grows her own feelings for Haruka, and finally decides to live and let live. Character arc.
I enjoyed the series taken as a whole, it's just that all the flaws underlying the series (tone confusion, bland MCs) really came to a head in the last two episodes, on top of a lame ending.