Akari, Aika, and Alice return to Aria Company after practice to find their three mentors talking, and learn they once also did combined training but have seldom all met together since becoming Primas (full undines). In flashbacks, their mentors tell the story of how Alicia and Akira as Singles hear of Orange Planet's new prodigy; when they meet a Single from Orange Planet named Athena, Akira asks about this unknown rival, but Athena is unable to answer her. They invite her to train with them, and soon realize that Athena is neither as graceful a rower as Alicia nor as adept a guide as Akira. However, when they practice singing one day, Athena's voice is so beautiful that passersby stop and applaud, and Akira realizes Athena had been the prodigy all along. In the present, Alice realizes that her trio will also break up after they become Primas, and Alicia tells her that it is important to enjoy the present and not regret what has been - or will be - lost. When Akari escorts Aika and Alice home, she begins to cry after they part ways.