By the way, it was brought up in like a panel of her manga, but Torako is herself an urban legend in-universe.
It wasn't elaborated on and the implication at the time was "haha comedy" rather than the supernatural elements of urban legends in MMaMD, but assuming this is the same universe there are probably 2chan creepypastas about her.
I don't know what that means when the origin of the urban legend is an actual normal person...well okay "normal" is a huge stretch, but she wasn't implied to be supernatural at the time.
Does that mean there's a separate Torako out there who's the manifestation of the legend? Or perhaps is she unified with the Oddity/Mystery? I don't know if that'd be different from being a person affected by an oddity, like Shizuku becoming the Little Girl in Red.
To begin with, maybe not all urban legends become Mysteries.