In the "Naruto" series, the "Grass Long Sword" refers to a particular weapon known as the Kusanagi Sword. The Kusanagi Sword holds great significance in the series and has ties to the character Orochimaru.

Orochimaru, one of the main antagonists, possesses the Grass Long Sword or Kusanagi Sword. It is a legendary weapon that is associated with his abilities and powers. The sword is depicted as a long, curved blade with a silver hilt and a snake motif.

The Kusanagi Sword is known for its ability to cut through almost anything, including steel and other materials. It possesses unique properties and is a symbol of Orochimaru's power and his connection to snakes and serpents.

Throughout the series, Orochimaru uses the Kusanagi Sword in his battles and incorporates it into his fighting style, utilizing both physical strikes and various ninjutsu techniques in conjunction with the sword.

It's important to note that the Kusanagi Sword's name and its association with Orochimaru in the "Naruto" series draw inspiration from the Kusanagi-no-Tsurugi of Japanese mythology, but the depiction and abilities of the sword in the series are unique to the fictional world of "Naruto."