This chapter presents a detailed analysis of the Sasebo landslide, which occurred on September 17, 2023, in Kosaza Town, Sasebo City, Nagasaki, Japan. The study builds upon the theoretical methods and governing equations introduced in previous chapters. It incorporates field borehole data to investigate the mechanisms of slope failure. The results show that considering the heterogeneity of weathered soils significantly improves the accuracy of numerical simulations. A Weibull distribution is applied to represent the variability in soil cohesion c and elastic modulus E. This approach leads to numerical simulations that closely replicate the actual failure patterns observed at the site. In addition, this chapter compares the results of both two-dimensional (2D) cross-sectional and three-dimensional (3D) slope stability analyses. The comparison highlights the significant influence of spatial variability within the weathered layer on slope behavior. These findings reinforce the necessity of accounting for soil heterogeneity in slope stability assessments under rainfall conditions.