The Metamaterial Optical Camouflage mantle refers to a very rare mantle with a Metamaterial Optical Camouflage (メタマテリアル
The mantle has the Metamaterial Optical Camouflage ability that hides the user from the eyes of both players and monsters by refracting the light that shines on its surface and is said to be the ultimate camouflage ability, which only a few high-level boss monsters have, in the game. The ability also allows the user to cloak their weapon after preparing it, making it possible for the user to shoot while invisible. Additionally, the cloak prevents the user from being detected by the Satellite Scan during the Bullet of Bullets tournament. The ability of the mantle also works within towns.
Like the Accuracy International L115A3, Sterben acquired the sniper by purchasing it from the game's RMT system using his monthly 500,000 yen allowance before the beginning of the 2nd BoB in September 2025.
Originally, after Sterben bought the mantle from the RMT, he only used it to practise ways of obscuring himself from others and tailing someone from behind because he felt that it was interesting to do so. However, one day, a person he was tailing went to the presidential estate to operate a game terminal. Using binoculars, he was able to see personal details inputted by the player, including his real name and address. Sterben memorised the information on instinct and wrote it down after logging out. As the ability to discover information about the real person behind the player made him happy, Sterben spent many hours in the presidential estate, waiting for players to put down their personal details, and managed to obtain the details of 16 players this way.
On a certain day in October, Shouichi’s brother Kyouji complained to him that the fake information spread by XeXeeD had ruined Kyouji's avatar’s development. Shouichi remembered that he had the real name and address of XeXeeD and told it to Kyouji. This eventually led to the «Death Gun» plot.
During the 3rd BoB, Sterben used the mantle to hide himself during the satellite scans, preventing other players from being able to detect his location. He also used the mantle to sneak up on his chosen targets in the tournament without being seen and use a stun bullet with his rifle to temporarily stun them, so that he could approach them in close range and imitate a murder with his Type 54 "Black Star". After killing Pale Rider in such a way, he used the mantle to escape the scene before Kirito and Sinon could catch up to him. He later used the mantle to set an ambush on Sinon inside the city ruins and stun Sinon with his stun bullet so that he could kill her with his «Death Pistol», but Kirito interfered before he could do so. Finally, in the desert, Sterben used this mantle to sneak up on Kirito and Sinon's position without being detected, though his attempt to kill Kirito before he was detected failed, as Kirito managed to avoid the bullet. Later, when Sinon tricked Sterben by using her Bullet Line to imitate a phantom bullet, causing Sterben to instinctively dodge the phantom bullet, he tried to use the mantle to escape, but his attempt failed when Kirito fired his FN Five-Seven at him, destroying the mantle.