Why did Ishiguro write this novel as a female?

Ishiguro was asked this in an interview. Here is his reply,

"I didn't worry much about using a female narrator. My first published novel, A Pale View of Hills, was narrated by a woman too. When I was a young writer, I used narrators who were elderly, who lived in cultures very different from my own. There's so much imaginative leaping you have to do to inhabit a fictional character anyway, the sex of the character becomes just one of so many things you have to think about–and it's probably not even one of the more demanding challenges. "