Who is “Johnnie Walker” in “Kafka on the shore”?

First of all thank you Mr. Murakami for taking the time to answer our questions. It's meaningful for us, readers, that writers make things like this. To be honest I've only read one of your books ‘Kafka on the shore’- but that was enough for me to become a fan of your writing. I'm about to read 'After Dark' and I'm very excited about it.

My question is about 'Kafka on the shore', it is supposed that Nakata took Kafka's place when murder was committed, but, who Johnnie Walker actually/really is? Kafka's father? And why is that Crow attacks him so hard at the forest?
I really appreciate your effort for responding my question. Greetings from Mexico.
(Hiram Martinez、男性、Student)

I’m sorry. I really don’t have any idea regarding those “mysteries.” All I can give you is just a story. And you have the right to think, to suspect, and to imagine. No public answers. You will have to find your own theory. Try.