First time poster here. Nice to meet all of you.
Unless you are Alto Saotome then your point is moot.
I see that Ranka is not really popular here, but from the looks of things, Alto will choose Ranka. The events will surely push these two together regardless of the outcome. So even if they have a tragic end, the plot will bring them together much like in Galia arc. I don't even think Alto had a change of heart after how he acted towards Ranka in episode 13. It's more like an awakening of something that was already there only to go back to sleep again because Alto is dense.
Don't get me wrong. I like Ranka and I like Sheryl. Sheryl is more of a big sister to Ranka and understands her. She may be even aware that Ranka likes Alto, so I think that Sheryl will act like a big sister to Ranka and let her have him. Sheryl, to me, is the one destined to sing for a greater cause. The heroine that will love all the people and sing for them. This is an astounding character development for someone like her who had shown no concern for her endangered fans when Alto informed her. She now have a broader perspective because she had to fall off her high horse and was able to see things from the bottom. After watching episode 20, I therefore conclude that Sheryl doesn't belong to one man. She belongs to herself and her music, while Ranka would rather want to belong to Alto even if her fate is with the Vajra. I hope Sheryl doesn't die. I hope Ranka doesn't leave with the Vajra. And with that *cue Lion OP theme*