Bincho-tan is the main character of her namesake anime, a young girl who lives alone in an old, traditional house situated far from town. She is easily recognized by the single piece of charcoal she wears on her head, a direct reference to her name, which is a play on the word for a high-quality Japanese charcoal known as binchōtan. Bincho-tan is typically depicted as being the size of a small child, but she possesses the notable ability to change the size of her body. This power allows her to shrink down to a very tiny scale, small enough to fit inside a shoe or to ride on the back of a duck for transportation.

Her background is marked by solitude and a sense of mystery. She lives by herself with no parents or guardians present, leading to the assumption that she is an orphan. She avoids answering shopkeepers who inquire about her mother, reinforcing this idea. Her only known relative is her grandmother, who has passed away but left behind a treasured set of clothes that hold significant sentimental value for Bincho-tan and become an important plot point. Her daily habits, such as greeting and bidding farewell to herself when she comes and goes from her home, further emphasize her isolated living situation.

In terms of personality, Bincho-tan is initially portrayed as a very lonely person. Despite her solitary life and the hardships she faces, she is also a hardworking and resourceful child. Each day, she travels to town to find work in order to earn money and buy food and other necessities. She is willing to take on a variety of odd jobs, including deodorizing shoes and refrigerators, showcasing her diligent and earnest nature. Although her life is difficult, she is generally sunny and finds joy in simple things, such as her favorite television character, Pukashuu. Her primary motivation is simply to survive and maintain her humble, independent life, all while cherishing the memories of her grandmother.

Bincho-tan's role in the story is the central figure through which the gentle, episodic narratives of rural life are explored. Her journey is one of gradual emotional development as she emerges from isolation. Her first significant friendship is with Chiku-tan, an enthusiastic inventor who helps her when she is injured. This meeting leads to a fast friendship, and they eventually begin raising a stray dog together, naming him Saji. Through Chiku-tan, Bincho-tan's social circle expands. She also attracts the attention of Kunugi-tan, a lonely rich girl from a mansion who becomes fascinated with Bincho-tan's simple life and freedom. Despite their different circumstances, they develop a meaningful connection, with Kunugi-tan even teaching Bincho-tan how to write. Other key relationships include Ren-tan, a miko at a Buddhist temple who can communicate with spirits, and Aroe, an aloe-haired girl who often suffers comical misfortunes. Through these interactions, Bincho-tan transforms from a lonely orphan into a child surrounded by a caring community of friends.