Edited by: Kazutaka Mannen, Diana Roman, Graham Leonard, Stephanie Prejean, Mitsuhiro Nakagawa
Hakone volcano, located 100 km west of Tokyo, Japan, is a hot spring resort area and one of the most popular tourism destinations in the country, with over 20 million visitors every year from all around the world. Although there is no historical record of eruption prior to 2015, frequent and intense earthquake swarms have occurred beneath the volcano. The 2015 eruption was a small phreatic eruption and only 100 tons of fine ash was released. However, precursory unrest began two months before the eruption and the entire precursory sequence was monitored in detail using densely distributed seismic and geodetic instruments. This special issue aims to compile multidisciplinary observations and understanding of this eruption and volcanic system and similar volcanoes worldwide to provide a basis for volcano monitoring and hazard mitigation in hydrothermal-prone volcanoes.