A-Cup Angst: The crux of Yukari's arc in the episode is that she feels inadequate in her younger proportions, thinking Tsukune's lack of interest in her is purely physical in nature.
An Aesop: Obsessing over your appearance (especially to impress a boy) will only make you miserable. Be comfortable in your own skin as it is.
Always Someone Better: Even with Yukari's newer, more attractive proportions, Kurumu's cup-size and height still beat her (even by a little), causing her to ask Mako to give her another dose.
A Day in the Limelight: The entire episode is centered around Yukari and her personal character growth.
Demoted to Extra: In the manga, Mako Yakumaru was a monstrel and a member of ANTI-THESIS sent as an assassin to kill Tsukune with her mind control fluid. Here, her species is never said, she only uses her abilities just to feed off of Yukari's insecurities literally and the exciting fight happened off-screen.
Does This Remind You of Anything?: The effect Mako's fluid has on Yukari is not unlike that of a growth spurt, having grown several inches and older proportions within the span of a nap.
Dramatic Irony: The main reason why Yukari wanted a hotter body was to attract Tsukune, but he is literally the only guy in school who doesn't want her.
Faux Affably Evil: Mako only helps Yukari in giving her a more attractive appearance because she knows that the realization that it doesn't magically fix her insecurities will be all the more devastating.
Irony: The only fan of Yukari's that doesn't like her new body is Kubasaki from "Farewell and a Vampire", who was her only admirer at the time.
