Event dating ri
A character with the exact same name appears in A girl that Koyomi has shared a class with since at least his first year.
She hates him utterly for apparently being better than her at math.
The characters who don't look up to her tend to remark on being unnerved by her perfection, finding it to be "unnatural".
In (Tsubasa Family), Koyomi discovers that Tsubasa's guardians are abusive, and she is possessed by a cat spirit that attacks and nearly kills random strangers every night as a way to deal with her stress.
She's very malleable, fickle, short tempered and lacks a sense of consistency, which is most easily seen with her hair being in a different style during every appearance.
She is the focus of Hitagi is a classmate of Koyomi's (and has been for three years), though they have never spoken before the story begins.
She has been in love with Hitagi since middle school, and has a pretty sizable fan following of younger girls.
After her own first arc, Suruga helps Koyomi and Nadeko out during the events of "Nadeko Snake", and continues to make minor appearances in the arcs following that.
Her personality is quite mysterious, but she knows a great deal about many situations and appears to be rather malicious.
She slips and falls down the stairs one day, and Koyomi, who is climbing them, catches her—only to realize that she barely weighs anything.