This is Susanô who retrieved the original Kusanagi no Tsurugi from the tail of the hydra and gave it to his sister, who gave it later to Ninigi no Mikoto the first « godsend » ruler of Japan. This Tsurugi with the mirror and the jewel are the three regalia proving the divine mandate given to him. They are the symbol of the Imperial rule over Japan.
Ninigi’s great-grandson Jimmu, was to become the first Emperor.