This paper focuses on packaging design using origami techniques, specifically designs incorporating curves, known as pillow boxes. While conventional paper packaging boxes are typically cuboid, pillow box designs include curved surfaces, offering both aesthetic and practical advantages. This study analyzes the specific curved folds of pillow boxes, clarifying the fundamental geometric condition these curves must meet. Additionally, it proposes new design variations for pillow boxes based on the condition. The relationship between the shape of the folds and the volume of the final three-dimensional shape is also explored. This research extends the boundaries of functionality and aesthetics in origami design and explores new possibilities in packaging solutions.