<p>The self-similar layered honeycomb structure, recognized as an effective design methodology for enhancing structural impact resistance, has predominantly been examined concerning lateral impact resistance in contemporary research. The mechanical properties and deformation modes of the honeycomb structure demonstrate significant variations under both in-plane and out-of-plane loadings, with the strength and impact resistance under out-of-plane loading being markedly superior to those observed under in-plane loading. However, there exists a distinct lack of systematic and comprehensive research regarding the influence of relative density, loading speed, and microstructure on the crushing behavior of in-plane rhombic honeycomb structures. Consequently, this paper presents an innovative design and research initiative focused on the rhombic honeycomb enhanced by self-similar inclusions (RHESSI honeycomb), systematically analyzing its impact resistance characteristics in the in-plane direction. Specifically, the paper undertakes a design analysis of structures with varying relative densities and conducts an in-depth investigation of impact resistance indicators across different loading speeds. Furthermore, it examines the deformation mode of the structure under in-plane impact and calculates the optimal wall thickness to enhance the energy absorption characteristics of the structure. It is believed that as the hierarchy increases, the CFE of the structure increases accordingly, with the maximum increase reaching 104.66%; meanwhile, the IPCF decreases, with the maximum decrease being 50.49%. This research provides an idea for the design and optimization of a new type of lightweight and thin-walled energy absorption structure.</p>