Item from Sword Art Online by Reki Kawahara
Kirito's Underworld blade — a sword grown from a branch of the Gigas Cedar that carries the memory of a tree that took seven years to cut down and a friendship that took less to change everything.
The Night Sky Sword was crafted from a branch of the Gigas Cedar — the impossible tree that Eugeo spent seven years chopping. It carries the tree's accumulated memory, which translates to enormous stored energy for Sacred Arts and memory release attacks. Kirito wields it throughout the Alicization arc, and it becomes the partner sword to Eugeo's Blue Rose Sword. Its memory release — Release Recollection — transforms the blade into a void of darkness that absorbs light and attacks, reflecting the tree's nature as something that endured everything thrown at it and remained standing. The sword is Kirito and Eugeo's friendship made tangible: born from their shared labor, carried into battle together.
A black longsword carved from the heartwood of the Gigas Cedar. The blade has a deep, starless black color — the 'night sky' — with occasional flickers of light along its edge, like distant stars in darkness. It feels alive in the hand, warm despite its color, and heavier with memory than its physical weight accounts for.
Also known as: Night Sky Sword, Black Sword