Multibeam bathymetry and track line geophysical data (magnetics and gravity) were collected in the Mado Megamullion oceanic core complex and the adjacent areas. The data were obtained between 2018 to 2021 during five cruises; R/V Yokosuka (JAMSTEC) YK18-07, YK19-04S, YK20-18S, YK22-18S, and R/V Hakuho-maru KH-18-02. The survey covers the oceanic core complex and the adjacent area from 138°20'E to 139°40'E and from 22°50'N to 24°50'N. The bathymetry was collected by EM122 (12kHz) and SeaBeam2020(20kHz). The total magnetic field was measured using a proton precession magnetometer towed behind the ship. The gravity measurement was done only in YK18-07 cruise using Lacoste-Romberg S-63 shipboard gravitymeter. The main objective of the series of surveys is to reveal the back-arc spreading process and the relationship with melt generation beneath.