  In the present paper, the current efforts in heavy-ion collisions toward
high-density nuclear matter will be discussed. First, the essential points
learned from RHIC and LHC will be reviewed. Then, the present data from the
STAR Beam Energy Scan are discussed. Finally, the current efforts, NICA, FAIR,
HIAF, and J-PARC-HI (heavy ion) are described. In particular, the efforts of
the J-PARC-HI project are described in detail.
