Shizuka Kikuchi started out as basically a throwaway joke character. Nube brings an Ichimatsu Doll to class and uses Shizuka—a quiet girl with long black hair—as the punchline to exorcise a possession. After that setup, she just kind of blends into the background with everyone else, usually hanging around with her best friend Noriko.
But there's more to her than just being scenery. A later chapter reveals that Shizuka's actually been using her low profile to spy on her classmates and report them to Nube. She's got a pretty rigid sense of justice that trumps her friendships—which almost gets her killed when a dangerous youkai team comes after her in retaliation. So despite looking innocent and harmless, she's actually one of the more active "background characters" in the series, just in a way nobody really notices until it's too late.
Content compiled by AnimeList.moe from publicly available sources.
