For Kashiwa Sato, the straight line is more than a geometric element—it is the foundation of his philosophy and artistic expression. It embodies a pure form, an ideal beyond visible phenomena. In the natural world, true straight lines do not exist: the movement of water, the branching of trees, and the shape of clouds all flow into organic, curving forms. The straight line, by contrast, is a human construct and a discovered concept —one that has come to symbolize reason and order. Within Kashiwa Sato’s expression, the line is connected to light, and is visualized as color. From a physics perspective, light travels in a straight line through a uniform medium but bends and shifts under refraction, diffraction, and gravity. In other words, while the nature of light is inherently linear, it is also subject to influences from its environment—an interplay that expands the meaning of the straight line beyond its geometric definition. The movement of light along a straight path represents universal order and logic, while its change signifies the fluid multiplicity of reality. The line and light stand at the intersection of logic and sensation, concepts and the transient. In Kashiwa Sato’s perspective, the straight line emerges not merely as a form, but as a primal symbol—one that crystallizes the unwavering purity of the ideal itself.