If I Could Float Forever In Space and Breathe A Clump of Hydrogen

Separation.

Boku in A Wild Sheep Chase is separated from the sheep man. Toru in Norwegian Wood is separated from Midori and Naoko. Boku in The City and Its Uncertain Walls is separated from his shadow.  Every Murakami protagonist finds themselves drowning from their own, personal separation.

What is separation to Murakami? Is it a form of alienation? Yes, but that would be oversimplifying things to the extreme.

Separation is the causality of what once was, meaning, the thing existed at one point in one state before being split or broken apart into another. Toru was permanently separated from Kizuki, which then transforms into genuine feelings for Naoko. When Toru's feelings aren't reciprocated by a detached Naoko, his feelings transform into affection for Midori. A dialectical chain of movement; Toru's feelings are repeatedly torn and put back together in an attempt to rekindle his separated feelings.

Boku in A Wild Sheep Chase goes through an opposite development. Instead of embarrassing the chain of causality in his life, he attempts to reclaim his separation through the chase of the black-star sheep and the Rat. He chases after these beings in hopes of reclaiming what never existed, a false-reality in which he was once whole. The sheep promises to make him whole, bringing him into dasein, the being of "there". But alas, Boku never ends up becoming Boku, the complete, but continues to just be "Boku".

The Boku of The City and Its Uncertain Walls faces separation from his shadow. He allows his shadow to live and rot within the surreal, impossible city. As he let's go of it, time passes as Boku forgets feeling and memory. Time moves on without him. In doing so, Boku simply becomes a person with only a capacity for thought. He thinks, thinks, and thinks yet never lives, the primary job of his shadow. 

Like life itself, separation is diverse. Murakami's characters often deal with the consequences of striving for or against it, but it an inevitability. A flower can never bloom into reality if the pollen if it doesn't trust the wind. The same applies to humanity. One can never grow if they choose to break apart. Through the loss of sight does one truly learn to feel.

-DK