He is a mysterious Burst Linker whose name does not show up on the matchmaking list. Rust Jigsaw appeared when Silver Crow and Blood Leopard signed up for a tag match. Rust attempted to quickly dispatch the two with the use of his various saws, but thanks to Blood Leopard, he was defeated. Due to Blood Leopard's final attack on his avatar, he had a lingering pain in his right shoulder/neck region. Haru tried to follow Rust in the real world, but was cut off. Much later, Rust's actions when trying to get out of the match cafe would help Haru figure out how Seiji Noumi was keeping his name from the matching list.
(Source: Accel World Wikia)