An electron-temperature profile of approximately 1 keV at the plasma center, together with its sawtooth oscillation, was evaluated from the bremsstrahlung power spectrum using a soft x-ray diagnostic system during the JT-60SA integrated commissioning phase. The analysis indicates that the observed opposite-phase oscillations between high-energy and low-energy bremsstrahlung emissions in soft x-ray signals result from opposing changes in electron temperature and electron density or effective charge. On the basis of the absolute intensity of bremsstrahlung at distinct energy ranges, it was found that, during sawtooth crashes, the electron temperature decreased while the electron density and/or effective charge increased. Furthermore, changes in the profile of the product of electron density and effective charge suggest a possible inflow of electrons and/or impurities across the inversion radius. This result was derived from short-duration parameter variations during the sawtooth crash, while analysis of long-duration changes suggests that this inflow is likely driven by an inward pinch.