Sai Yukitsugu

Sai Yukitsugu (狭井 雪嗣), known as Itsuki (イツキ) in Gun Gale Online (GGO), is an original Sword Art Online game character and one of the main characters in Sword Art Online: Fatal Bullet. He is one of the most famous and top skilled players in Gun Gale Online and is the leader of the Squadron "Alphard". While he is seemingly a calm and carefree player, Itsuki is secretly on a constant search for something to excite him. This obsession leads to him becoming the main antagonist of Fatal Bullet.

Gun Gale Online
Itsuki has a red- and narrow-eyed avatar with dark grey hair. His outfit prominently features black and white colours, with red seams overall. The inside of the arms of his long-tailed coat are light blue. He carries gun shells on the side and back of his coat. His canon choice of weaponry is a Dragonfall that resembles a real life Dragunov Sniper Rifle as his primary and a Sirius Optical Sub-Machine Gun as his secondary.

Personality
Itsuki is a mysterious character who is never willing to share anything regarding his real personality. Instead of being an open character, he enjoys providing various bits of information about himself, before promptly following up by claiming that he was joking, thus even his Squadron members do not know much about him. Aside from this, he is a skilled leader and a genius player when it comes to laying decoys and traps in GGO.

Towards the end of Fatal Bullet, Itsuki opened up to the Protagonist for the first time, confessing to the boredom he feels, as well as revealing that the only thing in the world that had sparked his heart was them. In the final chapter of the game, he admitted that he had desperately longed for the Protagonist's utmost friendship, to the extent that he did not care for anything that could pose a threat to that, going as far as creating a devious plan that could kill himself, the Protagonist, Kureha, and Zeliska.

Fatal Bullet
While on his way to enter a tournament implemented as part of a special update to GGO, Itsuki noticed Kureha and the Protagonist also registering for the event. Having heard of Kureha's reputation, the man decided to approach the pair to assess their potential, during which he learned the Protagonist had only begun playing GGO that very day. Impressed with the latter's resolve to participate in the tournament despite their inexperience, Itsuki expressed his wish to face them in the competition, before taking his leave.

Shortly after the start of the tournament later that day, Itsuki unexpectedly encountered Kureha and the Protagonist again while navigating the tournament dungeon with his companion Python. Although tempted to fight the duo, he decided it would be too easy to defeat them for the fight to be worthwhile. Instead, he sent them ahead to handle a difficult enemy deeper within the dungeon, promising to not pursue the two if they could defeat it. After Kureha and the Protagonist managed to vanquish the monster, Itsuki and Python parted ways with them at a fork in the path not far ahead, with the man giving the Protagonist first choice of which route to take.

To Itsuki's disappointment, the route he chose was filled with traps that weakened him and decimated all his other companions, which left the man unprepared when he encountered Kirito the Photon Sword Wielder and his partner Asuna. Only surviving the fight with the pair due to the tournament's duration expiring, he was automatically transported to the SBC Glocken, where he was reunited with them alongside Kureha and the Protagonist. To his shock, Itsuki learned the Protagonist had acquired a rare Type-X ArFA-sys unit. Bemoaning his own misfortune, the man nevertheless congratulated the new player on their accomplishment but declined Kirito's invitation to a party to become better acquainted with each other, explaining he needed to meet with his companions from the tournament.

Not long afterwards, Itsuki encountered the Protagonist once more while they were exploring SBC Glocken. Having seen footage of the Protagonist attempting to protect the ArFA-sys unit from Kirito during the tournament, he felt compelled to inquire the new player why they did so. Surprised by the Protagonist's honest answer that they were simply moving on reflex, the man took his leave to ponder on what he had learned.

Sometime later, Itsuki and Python noticed two players harassing another in the streets of SBC Glocken, with Afasys, Kureha and the Protagonist viewing the confrontation nearby. Overhearing Afasys's and the Protagonist's willingness to intervene on the tyrannized player's behalf, the man decided to accommodate their desire by forcing the bullies to retreat, then handed to Python a recording of the incident to be given to the game administrators to discourage further trouble. Afterwards, as he had attempted to converse with the Protagonist earlier but was forced to leave, Itsuki invited the trio to Alphard's headquarters. There, they discussed what motivated each of them and other people to start playing GGO. Upon learning the Protagonist had no special reason to continue playing the game, the man suggested that the new player join Alphard, sensing their potential and hoping to discover more about them, though he settled for adding each other to their friend list when the Protagonist declined the offer. Thereafter, he was able to join them on their adventures.

Following a brief unexpected visit from Zeliska and her ArFA-Sys unit Daisy immediately prior to the release of the SBC Flügel, Itsuki gathered in Kirito's residence along with the boy's friends to discuss their next course of action. Having decided to first send a scouting party to ascertain the difficulty of entering the ship, the man drew lots with the others to determine who would accompany Afasys and the Protagonist on the mission, only to lose the position to Kirito and Kureha. Once Afasys and the Protagonist succeeded in gaining entry to the new area despite some initial severe difficulty with handling the Gatekeeper boss guarding the SBC Flügel, Itsuki elected to resign leadership of Alphard to Python so he could form a new squadron with the Protagonist for convenience of access to the ship. Despite being criticized by the other Alphard members for not consulting them on the matter beforehand, the man abided by his choice but assured them he would eventually return.

Shortly afterwards, Itsuki joined the other members of the Protagonist's squadron as they began their expedition into the SBC Flügel, during which the group temporarily split into smaller teams for quicker exploration. While traversing the ship's bow alongside the Protagonist, the man noticed what seemed to be a teleporter trap. Out of an impulse to test his companion's trusting nature, he tricked the Protagonist into activating the trap while he remained out of range, sending his partner to a different area of the dungeon; once the Protagonist managed to return, Itsuki claimed he was unable to follow after them due to being occupied with another trap he accidentally triggered. To his surprise, the other player easily accepted his explanation, causing the man to momentarily wonder how far he could push their limits.

Having rejoined the rest of the Protagonist's squadron, Itsuki eventually encountered a sealed door that blocked access to the deeper levels of the SBC Flügel. In the process of searching for keycards to unlock the door, Itsuki and the others decided to briefly return to SBC Glocken for a break. As they entered a bar for refreshments, they noticed one of the bar's monitors streaming an MMO Stream broadcast featuring XeXeeD. While watching the program, the group witnessed a cloaked player approach the holo-panel and accost XeXeeD for his haughty attitude, before shooting at the screen with a pistol. To everyone's surprise, XeXeeD abruptly disconnected with a pained expression almost immediately afterwards, as if he had been killed by the mysterious player's bullet. Sensing the entire affair was more than just a stunt, Itsuki attempted to follow the cloaked player while everyone else was distracted by what happened to XeXeeD but lost him outside the bar.

Sometime later, Itsuki was contacted by Kirito to visit him in his residence, where the boy requested him and the rest of the squadron to discontinue playing Gun Gale Online for a while. When everyone pressed him for an explanation, they learned that XeXeeD and another famous player named Usujio Tarako had died in real life while apparently in FullDive, supposedly as a result of being shot by the same cloaked player, who called himself Death Gun. Recalling what he had seen with XeXeeD earlier, Itsuki relayed everything he knew about the event to Kirito. Although all the man could identify from Death Gun's avatar was his height and body type, as well as the handgun he had used, he deduced from the mysterious player's speech that Death Gun was likely targeting famous players, including himself. Intrigued by Death Gun's apparent power to kill people from within the game and willingness to use it, Itsuki stepped outside for a moment to collect his thoughts. After a conversation with the Protagonist regarding what they had heard, he decided to not stop playing GGO temporarily, as he was interested in how relatively calm Kirito and his friends were about the situation and wanted to see how they intended to handle it.