Why is Mai allowed to wear stockings at school? In Aobuta (&quot;Rascal Does Not Dream of Bunny Girl Senpai&quot;), the titular bunny-girl Sakurajima Mai is shown wearing stockings while attending school.



It doesn't seem like this is a part of the regular school uniform, since no other female student in the school is seen wearing stockings.






How is Mai allowed to wear stockings at school? Is this just artistic license to distinguish the main character in the series, and/or indicate her celebrity status/background? Or, are (some) schools in Japan lax about their dress code to this extent?
The regulations on school uniforms in Japan vary.
Considering Japan is experiencing 4 seasons and hence, winter season, some schools allow tights on cold weather while others outright ban them.
Some questions on Yahoo! Chiebukuro that supporting if wearing tights is allowed:

Is it weird to wear tights under a school uniform? (Japanese) (November 2010)
What is the best denier1 for tights under a school uniform? (Japanese) (December 2017)

1 Denier: a unit of measure for the linear mass density of fibers
While some schools outright banned them (and even made into news internationally):

Schoolgirls being told &quot;tights are banned!&quot; in a cold winter by their school become a hot topic (Japanese) (February 2019)
Japanese school explains why it won't let cold schoolgirl wear tights under her skirt (December 2018)

There are also some that require the students to wear tights in certain conditions even in spring/summer, like wearing black (and only black) tights for skirts above the knees.

Is it weird to wear tights in spring/summer? (Japanese) (June 2015)


Moving to the main topic...
There is no detail about the regulation for Mai's school, so it can be assumed that it is leaning to the looser one.
However, while the specific reference is not mentioned, the Japanese Wikipedia mentions that

芸能活動の支障にならないよう日焼けを防止するため、夏でも大抵黒のタイツを着用している。
To prevent sunburn which may hinder her living as a celebrity talent, she also wears black tights even in summer.
(Emphasis added)

This is somewhat strengthened by her character introduction in Dengeki Bunko's heroines in swimsuit

日焼けを気にして、デートでもなかなか素肌を見られる機会がないが、今回は、ファッション誌の撮影のために水着を着用。
Concerned about sunburn, while her skin is rarely revealed even while dating, this time she is wearing a swimsuit for a fashion magazine photo-taking.
(Emphasis added)