The 2016 Kumamoto Earthquakes, Japan, caused a number of geo-disasters in the Aso Volcanic Caldera, including a large-scale flow-type slope failure known as the Takanodai landslide. Between April and October 2016, the First Author conducted a series of post-earthquake geotechnical damage surveys and field investigations in the affected areas, and retrieved samples of volcanic soils. Following a detailed laboratory soil characterization, a numerical investigation including dynamic soil response and seismic slope stability analyses were performed by using the Quake/W and Slope/W software. In this paper, the results of the numerical analyses are presented and discussed. The numerical investigation indicated that the pumice soil deposit was responsible for the landslide triggering, and that the key factors for the flow-type failure were a combination of large inertial forces (i.e. shear stresses) and significant excess pore water pressure generation.