I'm guessing the pocket came unstitched. The mascot fell out because the pocket broke - which is also the same reason she was able to reach through the pocket to what was below.
They call it a "tail", but it's actually the mascot character's panty string that escaped her skirt in the same way as her owner.
Skirts can and do have pockets. You're probably confusing that with women's pants often having useless or non-existent pockets.
Is that a russian badger reference?
Interesting! With manga/anime overwhelmingly showing skirts and dresses you'd easily forget women ever wear pants in Japan in the first place. I suppose part of this is primarily because the industry wants to focus on teens so school uniforms are the general clothes and 'making girls look cute in casual wear in feminine clothes' is the secondary reason. Maybe illustrators/authors are mostly men and that leads to a wish-fulfilling designs (or they're just NEETs and don't hang out with women irl? if not, maybe the industry should stop spreading this stereotype like it's propaganda).
for realIt's more questionable why someone made the tail so similar to women underwear.
