A witch, and the youngest girl in the show.
Yukari is introduced in the third episode as an annoying little prankster that neither desires, or needs friends to make her happy. Seemingly content with all the misfortune that she causes others. Either by dropping giant brass pots on their heads, or by causing their skirts to fall off. It becomes rapidly apparent that as for a long moment in episode three where she is hanging from Moka's back, holding onto Moka's breasts. Eliciting a very amusing response from the men in the hallway.
At first, Tsukune finds her little more than an undisiplined, spoiled, bratty child. But after Moka tells him the nature of witches and the trouble that they go through, Tsukune is forced to revise his position.
This new perspective is immediately put to the test when Yukari is attacked by three lizard men that ambush her and break her wand, without which she is absolutly helpless. Tsukune dives, and tackles her out of the way of a slash from the lead lizard's claws, sustaining a large claw wound on his back. Vampire Moka then kicks the stuffing out of the lizards and they go back to the school. The next day Yukari claimes that she has fallen in love with Tsukune (dun dun dah).
In season two, Yukari begins to feel that, if she were an adult, that Tsukune would take more notice of her. The school nurse hears this and grants her this "wish". Yukari is then changed into a teenage girl with large breasts, although still not as large as Kurumu's to her great chargin. Despite her new "figure" Tsukune still does not seem to pay any more attention to her. The way the nurse says, it was because she was still a child at heart and the body could not change that. The rest of the group promptly arrives and beats the tar out of the nurse, reverting Yukari back to her little girl body. The change does SEEM to have some positive impact on her maturity.
Yukari has a very aggressive relationship with Kurumu, mostly over breast size. Yukari evens bites one of Kurumu's boobs in episode four during a pool event.
She is the object of affection of a perverted (he likes a ten year old girl for pete's sake) monster that has a stretchy neck This same monster expresses sorrow when Yukari is changed from a little girl into a young woman