This thought was in my head when I first saw the cartoon. So, I’ll share the AU of the plot: Sonata was the kindest of the three sirens, although she also sought to seize power, like Adagio and Aria, but it was more the influence of the other two sirens. In the end, Adagio got tired of Sonata’s endless naivety, so she was “excluded” from the gang, and the crystal was taken away to find a more suitable candidate. Sonata was hurt, bitter, and also betrayed by those to whom she was meekly devoted. But nevertheless, she finally felt free and will eventually be happy UwU