A high school drop-out since the age of 15, Kanehara pursued her passion for writing with the support of her father, Mizuhito Kanehara, a literary professor and translator of children's literature. She was born and currently lives in Tokyo.

She wrote her first novel Snakes and Earings when she was 21. The novel won the prestigious Akutagawa Prize (judged by acclaimed novelist Ryu Murakami), going on to sell a million copies.

In 2003, Kanehara was awarded the Subaru Prize for her novel Hebi ni Piasu (Snakes and Earrings); later that same year the novel won her the Akutagawa Prize, one of the most prestigious literary awards in Japan, making her and Risa Wataya the youngest people ever to receive this honor.