Rapid response ash fall surveys are necessary for evaluating the transitions and impacts of small-scale explosive eruptions that occur frequently at active volcanoes in Japan. Two key questions arise in such situations: (1) does restricted access to vent-proximal areas affect total mass estimates for ash-fall deposits; and (2) can data be collected and shared in a standardized manner to ensure efficient reporting of eruption phenomena during volcanic crises? We addressed these two questions by undertaking an ash fall survey following an explosive eruption that occurred at Nakadake first crater, Aso Volcano (southwestern Japan) at 11: 43 on October 20, 2021. The survey was conducted using the Japan Volcanological Data Network (JVDN) system for the first time, which allowed us to clarify the distribution and individual amounts of the ash-fall deposit and to test the utilization status and issues of the JVDN system under development. The October 20, 2021 ash plume rose up to 3500 m above the crater rim and was accompanied by pyroclastic density currents and ballistics in the proximal area. The ash-fall deposit was distributed along a SE-trending main axis, and was observed not only in the southeastern part of Aso caldera but also around Takachiho town, Miyazaki Prefecture (approximately 30 km from the source crater). During the three-day field survey conducted immediately after the eruption, we could only observe ash-fall deposits farther than 4 km from the crater. The maximum deposit mass was calculated to be 1300 g/m² and the maximum isomass line we could draw was 1000 g/m², therefore, the total amount of ash-fall deposits was estimated to be 13-15×10³ tons. In contrast, when taking into account the results of a survey conducted on December 22, 2021 in the proximal area (1-1.2 km south-southeast of the center of Nakadake first crater), the total mass of ash-fall deposits was determined to be 47×10³ tons. This value is about three times the amount obtained from the survey in the distal area (>4 km). The prompt sharing of information between the survey teams via the JVDN system enabled us to conduct an efficient ash fall survey, however, we also found various issues that must be addressed in the future.