The Japanese SWOT science team is an inclusive group for comprehensive studies on sub-mesoscale phenomena in the western North Pacific and marginal seas. (1) We compare coastal SSH variations in the Bungo Channel, Japan, with records of moored pressure gauges and GNSS height observations along ferry tracks. Although temporal changes in SSH at fixed points agree with in situ observations, spatial SSH anomaly distributions are physically unrealistic, mainly due to an insufficient coastal geoid model. (2) The 3D-Var assimilation of six conventional altimeters to the J-COPE model fails to represent locations and shapes of eddies that are detected by both the SWOT instantaneous SSH maps and trajectories of 115 surface drifters deployed east of Izu-Ogasawara Ridge (around 30N and 142E). However, temporal interpolation by the 4D-Var assimilation has relaxed this problem. (3) Compared with the 100-m depth temperature observed by ships and Argo drifters, the MOVE-JPN assimilation model using SWOT KaRIn data was worse than that with nadir data, especially in the Kuroshio Extension and eastern tropical Pacific. Possibly, conversion functions for the vertical thermal profiles from SSH are not well established for sub-mesoscale phenomena. (4) Assimilated results of river discharges from SWOT, based on its river widths and water surface elevation and slope observations, are better than those from Landsat’s river widths data, mainly due to the higher observation frequency of SWOT. However, in the areas well represented by the baseline model, the higher spatial resolution of Landsat results in better results.