Loggerhead sea turtles nesting off coasts of Japan are known to travel long distances throughout their life, however much of their behavior in the open ocean is still not clear. Argos transmitters were used to track 30 individuals. Low quality data were smoothed under a systematic set of criteria. Turtle behavior was divided into remaining, returning and departing. Relative velocity of the turtle with respect to ocean current was examined focusing on specific moments. In regions with strong Kuroshio currents, all turtles were drifted, however returning turtles were swimming against currents more often than those departing, indicating their unintentional drift. Around 150E, turtles either moved farther east or headed back the coast, in which currents were distinctly different for those south of the Kuroshio mainstream. Returning turtles heading back to the coast minimized energy consumption by swimming slower in warmer nutrient poor waters and against relatively weaker currents. Departing turtles in the Kuroshio extension bifurcation region were highly influenced by the currents and constantly headed toward higher regions of prey. Abrupt environmental changes could have a great impact on turtle behavior, however the degree of the impact would depend on the adaptability of the turtles.