This drama is based on the real-life struggles of a 15-year-old girl named Aya who suffered from an incurable disease, but lived life to the fullest until her death at 25. The script is based on the diary Aya kept writing until she could no longer hold a pen. The book that later followed entitled "One Litre of Tears" has sold over 1.1 million copies in Japan alone. Aya Kito proved her courage and positive attitude towards an uncertain future when suffering such an illness, spinocerebellar ataxia. The drama spans a decade, during which she graduates from school while her conditions worsen.