He felt agitated. Random, senseless thoughts flitted about his head. But all these thoughts were just variations on one theme. Like a man who has lost his sense of direction, Tsukuru's thoughts endlessly circled the same place. By the time he became aware of what his mind was doing, he found himself back where he'd started. Finally, his thinking process got stuck, as if the folds of his brain were a broken screw.
Some time ago, I wrote about Tolstoy's screw: an image of a mind stuck on a single idea that has been with me since I read War and Peace in my twenties. It was strange, but not surprising, to see this same image when I was reading Colorless Tsukuru Tazaki and His Years of Pilgrimage recently.