Fumiko is an Amanto of the Renho Tribe and an ally and former lover of General Eren aka Elizabeth. She desired to free her people from the tyranny of Dark Vader, making her an important ally during the Renho Arc. She is notably very flirtatious and perverted in nature, and tends to be sexually promiscuous with almost everyone, regardless of the situation, making her quite the sexual deviant.
Her costume looks like that of the average Renho, resembling a large white penguin/duck, however she wears a red bow, lipstick and eyeliner on her costume to show off her femininity along with a mole near the bottom left of her beak. She appears to wear little to no clothing underneath her costume as indicated by the reaction of those who have the pleasure of looking up her costume. Kagura describes her as having a "forest" between her legs.
Her actual appearance is that of a beautiful fair-skinned woman with red lipstick and makeup, long auburn hair and a mole near her bottom left lip. She is also seen wearing a blue jumpsuit when not in costume.
She is notably very perverse and is a self-described "slutty" individual, which she in fact is, and tends to engage in all manner of slutty acts around others, mainly those that involve masochism which appears to be her fetish. She will even offhandedly show off her goods to almost everyone, not caring if someone looks up her costume. Gintoki refers to her unique sexually appealing skills as "Slutty Magic". She also noted that she likes being on top.
Despite her promiscuous nature, she shows genuine concern for her people and Elizabeth as they were once lovers and wants nothing more than to see her people free from Dark Vader and find a new world to call home, and she will do whatever it takes to help her people, even nearly sacrificing herself to do it.
She was originally a Renho spy along with Elizabeth and many of her kind who infiltrated Earth to find out its weaknesses and hopefully invade it, however she never appeared to be fond of the idea and disliked the oppression her people suffered. She also used to be "Eren" Elizabeth's lover at one point.