Shirokuma

The Posh Russian Girl Preparing For Her Entrance Exams! Grrrolar!

A mysterious girl who starts living at the café where Hatsuyuki works while studying for her entrance exams. She claims, in fluent Japanese, to be a Russian polar bear, but her true identity is unknown.

She's extremely naive and has to rely on others for just about everything. She comes across as more of a rabbit than a polar bear.

Spoiler

Her real name is Mochizuki Takara (望月 宝), which she uses after being admitted to Shirosaki Gakuen two years later. She is called "Mochizuki-san" by her classmates, but her first name is never explicitly mentioned in the story.