The Nankai Trough is a locus of slow slips, low frequency, and large-magnitude classical earthquakes. It is assumed that high pore pressure contributes substantially to earthquake dynamics. Hence, a full understanding of the hydraulic regime of the Nankai accretionary prism is needed to understand this diversity of behavior.We contribute to understanding the full hydraulic regime within the Nankai accretionary prism by innovatively integrating the drilling and logging data of the NanTroSEIZE project. We focus on the toe of the Nankai accretionary prism by studying data from hole C0024A drilled during IODP expedition 358. This drilled hole intersected the Nankai décollement at 813 mbsf, about 3 km from the trench. Pore pressure was first estimated using Eaton’s method on both drilling and sonic velocity data. Both results show that pore pressure follows hydrostatics until the top of the hemipelagites, with local pore pressure rising up to 38% above hydrostatic especially crossing the décollement. Downhole Annular Pressure was also monitored during drilling, and a careful reanalysis of its variation shows the occurrence and the locus of fluid flow between the formation and the borehole. Primarily, there are two identified fluid flow anomalies intervals: (1) at the shallow depths <100 mbsf with loose coarse sediments, which could be related to erosional unloading, landslide, slope instability. (2) Below the décollement (<813 mbsf) at the two asymmetric damage zones. The damage zones at the footwalls of the major faults are predominantly permeable with significant porosity and permeability values with orders of magnitude between ∼10−16 to 10−17 m2 as quantitatively estimated using the Hvorslev equation for a fully penetrating well in a confined aquifer. Our results show that the formation fluids are getting significantly over-pressurized only a few hundred meters from the toe of the décollement. The décollement is already impermeable across the fault, and the fluid flow is channelized along the damage zones. The impermeable décollement acts as a hydraulic barrier inhibiting fluid flow upward, keeping high pore pressure at the footwall and increasing the structural weakness of the lithologies. It’s therefore probable that high pressure is also expected further down in the locus of tremors and slow slip events.