Eiji

A young man who ranks 2nd in the OS rankings and wields a straight sword. Born on April 8, 2006, with a blood type of B. At the time of the movie "Ordinal Scale," he is 20 years old and a student at Tokyo Industrial University.

He is a survivor of SAO, and his avatar name at that time was Nautilus. After losing Yuuna in SAO and surviving, he was faced with the harsh reality that his family had already dispersed and he had lost all connections in the real world. Disillusioned with everything, he lived a lonely life, but after being approached by Shigemura with the Yuuna Resurrection Plan, he resumed studying for exams, using the plan as emotional support, and began participating in Shigemura's lab as an auditor.

In OS, he is equipped with a special Augma given by Shigemura, which includes a muscle assist suit and action prediction function. His in-game ranking is 2nd, possessing skills far surpassing Asuna and Kirito. To advance the Yuuna Resurrection Plan, he continued to steal the memories of SAO survivors using physical attacks, sending all members of "Fuurinkazan," including Klein, whom he had no direct acquaintance with, to the hospital due to his growing hatred over the Yuuna incident. He was defeated in a one-on-one battle with Kirito, who rose again to retrieve Asuna's memories, and his suit was destroyed. Shigemura deemed him useless and set a SAO floor boss on him to recover Yuuna's memories, causing him to lose consciousness. He woke up just after everything had ended and couldn't even remember if his memory had been scanned.

After the Yuuna Resurrection Plan collapsed, he turned himself in to the police for assaulting the Fuurinkazan members and was in a delicate state of detention, unsure if he would be prosecuted. A week later, Kirito, needing his cooperation regarding a mysterious message, arranged through Kikuoka for his release without charges. As Nautilus, he infiltrated the old SAO server, received support from Kirito, and reached "Black Yuuna." At the place where Yuuna once lost her life, he witnessed the complete disappearance of "White Yuuna" and embraced the merged "Black Yuuna," crying.

In the anime version of "WoU," he overcame VR incompatibility and logged into ALO with Yuuna as his navigation pixie. Responding to Lisbeth's plea, he joined the inter-world war in UW. Even when cornered by Chinese and Korean players, he was nearly unscathed and challenged PoH to save Kirito. Though initially outmatched, he received a buff from Yuuna's song and fought PoH again, holding his own. Overcoming his past weakness, he took on the appearance of his Blood Knights era as Nautilus with his willpower, but after having both arms severed, he made a literal last bite and logged out, creating an opportunity for the Chinese and Korean players to realize PoH's true identity.