This study updates the mid-Cretaceous (100 Ma) paleomagnetic pole for the inner arc of the southwestern Japanese islands, referred to as southwest Japan, to investigate potential stagnation in its apparent polar wander path (APWP). The updated pole interpolates the Cretaceous APWP for southwest Japan, providing insights into the geodynamic characteristics of the region during this period. For paleomagnetic analysis, red mudstone samples were collected from four sites in the 100 Ma Hayama Formation in the Hayama area. A high-temperature remanent magnetization component, carried by hematite, was isolated from the four sites, passing the fold test. The primary nature of the magnetization was confirmed by the detrital origin of the magnetic carrier. The primary directions, combined with previously reported results, were used to define a paleomagnetic pole representing the 100 Ma pole for southwest Japan, located within the group of Cretaceous poles. The APWP for southwest Japan between 110 and 70 Ma was revised to evaluate stagnation in polar motion in this region.