Ko-ichi studies marine geology including hydrothermal and gas hydrate sites in various settings. Subseafloor fluid emission makes variety of geologic phenomena on the seafloor as well as variety of chemical and biological process in the water column. He joined the first 2009 expedition in the Cayman Trough utilizing HROV Nereus on the Cape Haterras with his electrochemical sensor (Eh sensor). In the succeeding RRS James Cook Voyage 44, Eh sensor on UK AUV Autosub6000 played major role in locating vent fields. Because of the very deep nature of the Cayman Trough, our data coverage in the water column both by CTD and AUV is still limited. He is expecting to find new vent field, which may coin world record of temperature and depth. In the cruise he will chase the hydrothermal plume by Eh sensor both on CTD and Nereus. He will also maintain the electrode and interpret data for the chasing efforts.