Dorama ini -1 Litre of Tears (1 Ritoru no Namida)- diambil dari kisah nyata, menceritakan ttg seorang Aya yang berjuang menghadapi penyakit Spinocerebellar Degeneration dari usia 15 sampai 25 tahun. Penyakit tersebut merupakan penyakit syaraf yang akan menurunkan kemampuan fisik secara bertahap, mulai dari kelumpuhan sampai kehilangan kemampuan menulis dan berbicara, bahkan untuk menelan makanan. Parahnya, penyakit ini tidak bisa diobati, sehingga selama bertahun-tahun Aya menghadapi penyakit ini , sementara itu kemampuan fisiknya mulai menurun dari hari ke hari. Selama itu, ia menulis apa yang dipikirannya dalam sebuah diary hingga ia meninggal pada 23 Mei 1988 12:55 am.

Original 1 Litre of Tears,

Ikeuchi Aya was a 15-year-old girl. She was Japanese. She lived with her parents, her brother, and her sisters. She was the oldest among them. Her father opened a tofu shop at their house. Her mother worked as a health consultant.
Until she reached the age of 15, she was very healthy and lively. She joined the basketball team in her junior high school as well as in her senior high school. She was really good at basketball and became a regular member as soon as she joined the team.
But at 15, she realized something weird was going on with her body. She fell really often when she walked and also couldn’t pick her bag up from the floor, when she wanted to put it into her school locker. Of course, for a normal person, this wouldn't happen.
Not only Aya, but her mother noticed it as well. So one day, when Aya fell again right on her face, her mother brought her to the hospital to cure her injury and also to have a general check-up. The doctor was a neurologist. He found that Aya’s cerebrum suffered from a degenerative condition. He soon told Aya’s parents. And for Aya, she found out by herself that she had an incurable disease named Spinocerebellar Degeneration.
From then on, Aya’s condition got worse and worse. She became just like the doctor said she would be. She became unable to walk and was forced to use a wheelchair at school, so she had to leave the basketball team. Then, it became very difficult for her to write. It made her lessons in class difficult to do. The teachers decided she must move to a school for the disabled. Sadly, she moved there.
Years later, she had to stay in the hospital because her condition made it impossible to live outside. From then on, she could no longer speak. It became difficult to write, and difficult to swallow food. In her 25th year, she left this world.
Now, her youngest sister, Rika, works as a private tutor teaching kids how to study; her younger brother, Hiroki, is working as a policeman, protecting the area and keeping it safe. Her younger sister, Ako-san, ever since graduating from Higashikou High School where Aya attended, like Shioka, has been working as a health consultant. Her father, Mizuno, and her mother, Shioka, up until now are still continuing to pass on Aya’s beliefs.
During her suffering, she wrote in her diary every day until she couldn’t write anymore. She said it was the only way to prove that she was still alive…

1 Litre of Tears Diary's,

My life is like a flower that hasn't bloomed yet.
From the start of this youth, I want to treasure it and have no regrets.

Okaasan. In my heart, I know I can always trust my mom.
From this point forward, I leave it for you.
I'm sorry for always making you worry.

This disease, why it did choose me?
Fate. It can't be put into words.

I want to make a time machine and go back in time.
If it wasn't for this disease, not only I could I enjoy falling in love but I also wouldn't have to rely on anyone and live by myself.

I really don't want to say things such as "I want to go back to how things were before".
I recognize how I am right now, and I will continue to live on.

Therefore I definitely won't run away.
That's what I'll do. Definitely, always.

Even if it's like that, I still want to stay here.
Because this is the place where I am.
To be able to be seen as an equal by my friends, I'm really thankful.
"We've started to like reading, under Aya's influence", they said.
"Ah! that's great". I didn'just only make trouble for them...
Thinking like this, I've started not mind it that much.

If you look up at the sky after falling down the blue sky is also today stretching limitlessly and smiles at me... I'm alive.
I'm alive.
There are still four days until school ends.
Seems like that because of me, everyone is folding a thousand paper cranes.
The looks they had when they were folding so diligently,
I'm going to keep them deep in my memory.
Even when we've been separated, I will never forget them. But... I'd rather hear them say "Aya-chan, don't go."