In order to monitor quantitatively magma transport process in Sakurajima volcano, the ACROSS system composed of two vibration sources was deployed in Sakurajima Island, and the system produced continuously the accurately controlled imperceptible elastic wave signal from 5 to 15 Hz. The signal from the ACROSS is routinely monitored by 15 permanent stations and 4 temporal stations in Sakurajima volcano. We successfully observed the ACROSS signal at each station and could detect temporal variation of the transfer function (TF). Because the temporal variation of later phases in the TF was obviously larger than that in the early phases, we inferred that the temporal variation of the later phases reflected the temporal change of the structure in deep regions beneath Sakurajima volcano. We also found that the temporal variation of the TF is correlated with volcanic activity such as the daily volcanic eruptions and crustal deformation in Sakurajima Island.