Abstract. Since 2012, seven perennial snow patches in the northern Japanese Alps have been determined to be very small glaciers (VSGs: <0.5 km2). However, it hadnot been determined how such glaciers could be maintained in such a warmclimate. In this study, we calculate the annual mass balance, accumulationdepth, and ablation depth of five of these VSGs, covering 2015–2019 forfour of them (2017–2019 for the fifth) using multi-period digital surfacemodels (DSMs) based on structure-from-motion–multi-view-stereo (SfM–MVS)technology and images taken from a small airplane. The results indicate that, due to snow acquired from avalanches andsnowdrifts, these VSGs are maintained by an accumulation in winter that ismore than double that from the snowfall, thereby exceeding the ablation insummer. Therefore, we classify them as topographically controlled VSGs. Wefind very small yearly fluctuations in their ablation depth; however, theirannual mass balance and accumulation depth have large yearly fluctuations.The annual mass balance, which mainly depends on the accumulation depth,showed accumulation throughout each glacier during heavy snow years andablation throughout each glacier during light snow years. Thischaracteristic differs from the upper accumulation area and lower ablationarea that exists on most glaciers. These VSGs lack a positive annual massbalance gradient, which suggests that they are not divided by a distinctglacier equilibrium linealtitude (ELA) into an upstream accumulation area and a downstream ablationarea. Moreover, compared to other glaciers worldwide, we find the massbalance amplitude of VSGs in the northern Japanese Alps to be thehighest measured to date.