---A young girl wakes up in a hospital while on a summer vacation trip.

Suddenly, she was told of her mother's death. She didn't believe what anyone told her.
"Where is my mother?"

The girl eventually runs away from it all, returning home alone.
But there was no one there.

"I finally understand," she said,
"My tears were falling onto the floor,
and my fingernails dug into my hands when I clenched my palms,
and it hurt. It hurts, it hurts. Ah, it's all so real."

Unable to accept a world without her mother, the girl hugged her knees and waited only for her mother's return.
She lived in uncertainty and loneliness, as if she were atop a castle in the sand.
She dreamed only of sinking into the sea, and these dreams gradually drove her heart mad.
"Mother, come home soon..."

One night, a stranger appeared before the girl's eyes.

Knowing that the girl had run away from the hospital, the man came to her house to coerce her.
"I will allow you to stay here, but I will keep an eye on you."

The girl is repulsed, but she can't escape.
"I can't go anywhere. I just want to stay here forever..."

There are only 10 days left until the end of summer vacation.
A girl and a man begin a strange life together.

[Translated from the official website]