Stix and de Moor (2018) compiled recent studies of phreatic eruptions and proposed two endmembers for phreatic systems. Type 1 systems are characterized by a sealed hydrothermal system. Injection of magmatic fluids causes pressurization of the hydrothermal system and eventual rupture of the seal, generating ballistics and fine ash. For a Type 2 system, input of magmatic fluids into a near-surface hydrothermal system vaporizes liquid water, promoting eruptions which emit wet ash, lahars, and or ballistics. Since injection of magmatic fluids and rupture of hydrothermal seals are key processes, monitoring of broadband seismicity and gas ratios is the most useful approach to forecast phreatic eruptions.the special issue on the 2015 eruption of Hakone volcano. They consider Hakone has a type 1 system referring to the chronology reported by Mannen et al. (2018).