Yeeesss, Episode 5. Most excellent choice.
Having seen Episode 12, it's almost tied with Episode 5 in my book. It was heart-wrenching seeing Sheryl having to suffer, but then watching Ranka charging in with speakers maxed-out balanced that out somewhat. The episode would have been fine without the cliffhanger, which took away from Alto and Ranka's alone-time. However, I have a feeling that the writers will want to have Alto and Sheryl share the sky together later in the story.