Kokubu Karin is a Grade 7 junior high school student attending Sei Ringo Gakuen. She has bright red hair that she wears up as a ponytail and, like the two wisps on her sides, has curly ends that reminiscent to a curly pig's tail. Karin also wears a ribbon with a blue ball, just on top of the pony tail.

Although Karin is klutzy, she has a caring heart. Because of this she helped Ton-chan in the first place, and that made him choose Karin as Buurin, the Pig Girl of Love and Courage.

Karin has a crush on Mizuno Kouichi, but he likes her alter ego Buurin. This caused worries in Karin. Her other worries came from her father, little Shuuhei, and later Jimmy Matsumoto, who are always on her tail when she appears as Buurin.