The upper Miocene Misaki and Nishizaki formations on the Miura and Boso peninsulas in central Japan preserve the deformation features of an off-scraped accretionary prism. The spatial distribution, geometry, and style of accretion-related deformation with paleotemperature and burial depth estimation are elucidated in this study. The deformation structures and textures are similar to those of modern accretionary prisms. The low maximum paleotemperature (<50¿C) and high preserved porosity of the sediments (30--50%) imply a maximum burial depth of less than 1000 m. On the basis of the mode of deformation, this off-scraped body is divided into an imbricate thrust, a thrust unit, and an upper coherent unit in ascending order. The imbricate thrust corresponds to a branch from the basal d¿collement zone and is subdivided into a brecciated zone, a main gouge zone, and a shear band zone. The thrust unit hosts a concentration of thrust systems that form various orders of duplex structures, while the upper coherent unit is characterized by gravitational instability- and earthquake-induced deformation without thrust faulting. The duplex distribution, shear strain, and fluid migration associated with the off-scraping processes are clearly localized within the imbricate thrust and thrust unit. This accretion-related deformation occurred before lithification of the sediment and under high fluid pressure induced by shear deformation, thickening of the sedimentary sequence, and earthquake-induced liquefaction. These processes are inferred to control the effect on the mode of deformation and the location of thrusting during early deformation of the accretionary prism.