I really enjoy the song myself. It's INSANELY catchy and just makes me happy everytime I listen to it.
Plus, everyone got at least one line. And yeah, Sayumi sounded bearable. Frankly, I was impressed. Plus, it's good that certain memebers didn't over dominate the song and we didn't hear a whole lot from them. Like Reina.
Plus, it's a really good introduction to Aika!