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An original character by Rakurakutei Ramen.
Classmate with Tamaryu and Ran, and whose teacher is Shizuki in the new Youkai school that opens up, she occasionally appears in class-related strips.
She is a white serpent youkai, probably a reference to The Legend of the White Snake (Wikipedia), and claims as her lover the rather unusual target of a frog-youkai boy. (This, in turn, is a reference to the Japanese belief in a rock-paper-scissors balance of frogs being weak against snakes, who enjoy eating frogs, while slugs are strong against snakes and weak to frogs.)
Sara enjoys talking about "eating" her "lover", Yanagiba Kiyoshi, in ways that one can only hope is suggestive.
She has a lamia's figure, and apparently goes without wearing underwear with distressing frequency. However, there's (usually) nothing there to see, and her belly scales cover anything up, so she apparently thinks nothing of going bottomless (even swimming without a bottom).
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