Best Girl has Blue Hair

Conjecture.

Let $G(A)$ denote the closed set of female characters in a series $A$, defined only if there is at least one $g \in G(A)$ such that $g$ has blue hair.

We postulate that there is a strong positive correlation between:

• $[P]$: $g$ is best girl.
• $[Q]$: $g$ has blue hair.

Intuitively, we claim that $P$ strongly implies $Q$, and vice versa: “most best girls have blue hair, and blue hair girls are often best girl”.

Definitions

• We use series to collectively refer to any film, animation, anime, manga, webcomic or similar visual media.
• $P$ states that in the partial order of favouritism on $G(A)$, $g$ is the maximal element.
• $Q$ includes any shade of blue, but overwhelmingly media use darker shades of blue for hair.

Empirical Evidence

Proofs

We identify the following series to satisfy the conjecture:

• Oshi no Ko: Akane Kurokawa, closely tailed by Ruby Hoshino.

• Domestic Girlfriend: Rui Tachibana clears.

• Close As Neighbours: May and it’s not even close.

• Arcane: Caitlyn and Vi would share, but young Caitlyn is way cuter than Vi and gives her the victory.

• Shikimori-san’s Not Just A Cutie: Kamiya is on equal footing with Shikimori.

  (In descending order of “how strongly I feel she is best girl”)

Counterexamples

However, the following series violate the conjecture:

• Yu-Gi-Oh: ARC-V: Sora is disgusting, and there are indeed no other blue-haired girls 💔
• Kanojo, Okarishimasu: Ruka, no thanks lmao