High-recovery core sample and downhole logging data from Sites 1150 (39 degrees 11'N, 143 degrees 20'E) and 1151 (38 degrees 45'N, 143 degrees 20'E), drilled during Ocean Drilling Program Leg 186, generally confirmed the Neogene tectonic erosion history as discovered and described by Deep Sea Drilling Project Legs 56, 57, and 87, drilled between 39 degrees 44'N and 40 degrees 38'N in the northeast Japan Trench forearc. We propose that the sedimentary characteristics of the drilled cores can be explained as consequences of the change in plate coupling between the subducting Pacific plate and the Eurasian plate, dependent on the plate dip angle and water flux resulting from plate subduction. Our model explains the interrelationship among the observed and inferred changes in the plate dip angle, location of the volcanic front, sedimentation rate, volcanic activity, and horizontal stress field caused by the change in plate coupling, which dictates the amount of tectonic force transmitted across the plate boundary. Previously studied subsidence history of the forearc, ascribed to the subduction erosion process, is also incorporated.