The advancement in terrain survey technologies and sophistication of terrain data are gradually enabling swifter estimation of sediment movement from landslide disasters. However, volume estimation of colluvial deposits in a collapsed area is impossible via simple differential analysis of precise terrain data comparing before and after the collapse alone, as this does not take into account the rupture surface below the colluvial layer. That estimation is crucial for avoiding secondary disasters during search and rescue operations. This paper presents the trial of the simulation of the rupture surface followed by swift estimation of the volume of colluvial deposits in the collapsed area from the slope failure at Yabakei on April 11, 2018. The trial used datasets obtained only from aerial surveys without conducting any field surveys in order to prioritize swiftness over accuracy. The trial was completed in just three days, and the hypothetical rupture surface was mostly consistent with the later reports provided after conducting field surveys.