A devastated world where the surface is contaminated by radiation and humans live in underground cities.
Children with normal reproductive functions are traded at high prices, and the protagonist, Line, was bought by a couple of cyborg researchers at a young age. She was
educated to become the wife of their only son, Wilm, and they married, but Wilm was sickly and could not have children.
Seeing Wilm getting weaker day by day, Line becomes increasingly anxious.
And when Wilm dies, he leaves an android, "Nine," for Line's future.

As Line begins to live with Nine, she suddenly feels that this is what it might have been like if Wilm had lived.
Although she is anxious about her future life, just as she begins to get used to living with Nine, an event occurs that changes Line's life completely...

"Line, you can't live without me, can you?"
What does her sickly husband leave behind...?