According to Kojiki
Susanoo スサノオ
Defeated Yamata no Orochi 八岐大蛇
A legendary eight-headed and eight-tailed serpent
And found a great sword in the fourth tail

Initially ‘Heavenly Sword of Gathering Clouds’
Ame-no-Murakumo-no-Tsurugi 天叢雲剣
Now ‘Grass-Cutting Sword’
Kusanagi-no-Tsurugi 草薙の剣
One of the three Imperial Regalia of Japan三種の神器
With the mirror and the jewel
Representing the virtue of valor

In Atsuta Shrine 熱田神宮 Atsuta-jingū in Nagoya