Close your eyes and try to locate where "you" are. Most people point behind their eyes, or somewhere in their head. Maybe in the chest. The location feels obvious. As if a small person were sitting up there, looking out. The person is so familiar you never question whether they exist.
K's claim is that the person doesn't exist. There's no homunculus behind the eyes. There's no executive in the chest. There is, instead, a center where thoughts have congregated. The center calls itself "me" because thoughts accumulated there, formed habits, started to seem persistent. The center is the accumulation, not a person experiencing the accumulation.
Out from the center radiates the periphery. The rest of life. Other people. The world. Stuff. The center evaluates the periphery, defends against parts of the periphery, reaches for parts of it. The structure makes the center feel like the protagonist and the periphery the setting. K reverses the assignment. The center is one tiny region of the field where thoughts happen to clump. The periphery is the much larger field they happen in.
When the center is treated as the protagonist, life is small and defended. When the field is treated as the protagonist, life is wide and the center is just where you happen to be standing for now. The difference shows up in the body. The defended center clenches. The wider field allows the breath.
There's no "you" at the center of your experience. There's a region of clumped thoughts pretending to be a person. The pretending is convincing only because no one has questioned it in a long time.