This project studied the basin evolution of the Kumano Forearc located offshore SW Japan. The primary dataset used was a 3-D depth migrated seismic volume and two wells drilled within the basin as part of an IODP project to study the characteristics of the Nankai trough seismogenic zone in which the Kumano Basin is located. The overall goals were to use seismic stratigraphy to interpret the lower stratigraphy of the Kumano Basin and to document the spatiotemporal evolution of the early basin sediment fill. Several sequences of packages were mapped within the lower forearc sub-units in the Petrel seismic interpretation program (created by Schlumberger). The inventory and file descriptions of the horizons, well tops, surfaces, isopach maps, and faults interpreted within seismic volume are provided in the listed documents.