The episode was actually interesting, as expected of this type of anime.
The first quart of the episode does a good job at showing us how lonely the main girl is. The second quart then begins with her walking though a dark underground structure from which she reaches a new light. This is the classic imagery of the rebirth in mystery cults. This is highlighted by the dance itself, which represent a non-verbal language that you need to be instructed on.
Buchou and Sayu represent two different types of feminine. Buchou is the ideal traditional woman in Japanese culture, but she is manipulative and clever. Sayu on the hand is raw sexuality, showy and unashamed.
They are the archetype of the woman the man fear, the tigerr they can't domesticate and the cat they think they domesticated.
As we saw, our MC was just born new and thus should be pure. But she has an original sin, one that she is aware of, that prevents her from being good enough to begin her training.
Also, noticeably, this sin comes from outside the world represented by the school.
We can conclude that this anime will be a sort of purgatory for our main character, when she finally sheds her past and is able to become a new girl.