Origami structures are lightweight and reconfigurable, creating 3D shapes by folding 2D facets. However, increasing bending stiffness in a 3D shape is challenging because the structure needs to undergo transformation, and the thin facets are easily bent. This problem is especially critical in an angled arm shape, which serves as an element of various configurations. Here, we propose a method that leverages origami transformation, which typically reduces structural stiffness. We combined two layers with the opposite folding motion. This induces interlocking due to opposite movements in the cross-sectional direction during axial bending, resulting in high bending stiffness. Based on this, we developed an arm support device, furniture, and a shelter that remain flat in their normal state but can easily transform into shapes with high load-bearing capacity.