The nuclear fusion reaction plays an important role in several phenomena in physics, such as the energy production in stars, nucleosynthesis, and a synthesis of superheavy elements. In particular, heavy-ion fusion reactions at energies around the Coulomb barrier are intriguing phenomena showing strong interplays between nuclear structure and nuclear reaction. For example, in medium-heavy systems, it has been known that fusion cross sections are largely enhanced relative to a prediction of a simple potential model, which has been interpreted in terms of quantum tunneling with many degrees of freedom. In this seminar, I will discuss quantum many-body dynamics of heavy-ion fusion reactions. To this end, I will summarize the current status of the field and will discuss future developments of nuclear reaction theory. I will put some emphasis on nuclear reaction for superheavy elements and will discuss future directions from a view point of multi-disciplinary science for systems in a strong Coulomb field.