Versus is the «Sword Art Online» and «Accel World» crossover published on December 10, 2011 in Volume 10 Chapter 3 of Accel World. It was also adapted into one of the tracks of Accel World + Sword Art Online Drama CD.
Summary
Kirito is on a part-time job to test out the 4th generation of Full Dive by RATH. He is told that othe users have seen a ghost and so he is there to check if it's true.
During the dive he sees a robotic figure. He instinctively grabbed the sword hung on his back, just to find out that he is the avatar from SAO, Kirito the Black Swordsman. He looks up and sees a timer, health bar, stamina gauge and on the left side [KIRITO] and on the right [SILVER CROW].
He tries to communicate and walks slowly forgetting he is still holding his sword. Silver Crow suddenly rushes and tries to kick him, Kirito dodges it swiftly. He draws out his Elucidator and while remembering the feeling of one of his old beloved swords, swings his sword without thinking, cutting Silver Crow's right shoulder. Silver Crow begins using his special move and flies out. Confused, Kirito looks up and sees that Silver Crow's stamina gauge, which was full before, had decreased by around percent. Kirito realises that this bar indicates the special move and that his special move must be a sword skill as he was Kirito, the Black Swordsman.
He tries to see if his guess was right and tries to do a basic one-handed straight swords skill «Sonic Leap» causing the sword to growl faintly and the stamina gauge shining part blinked, indicating that the gauge wasn't full enough. Kirito also realised that he was the one intruding and Silver Crow must have played this game daily and the 4th-generation experimental machine's quantum circuit intruded.
Silver Crow rushed in again while lowering his body and focused on the tip of the sword and while lowering his body even further, shortened the distance by 10 meters at once. Kirito tried to slash his sword upwards to intercept him, who was leaning forward, however Silver Crow opened his left wing, causing his body to rotate 90 degrees, only getting a shallow cut on his chest armor and he stepped on his left foot trying to make an uppercut to his abdomen but Kirito dodged it, only grazing his left shoulder, though Silver Crow used his left fist to make a short hook, damaging him. Silver Crow also used his right knee to successfully attack him and he pinned Kirito's left arm with his right and aiming short strikes with his left making Silver Crow think that the sword would be useless at this range however he realised that he didn't have his sword and he only had his right hand's fingers spread out and in a smooth but terribly fast movement Kirito touched Silver Crow's chest with his now emitting orange light right fist, making Silver Crow realise he was using his special move. There was a great impact on to Silver Crow as he was repelled backwards though the damage wasn't great. Suddenly Kirito rushed in empty handed and Silver Crow was wondering what he would do. Silver Crow realised that his right hand was still going, indicating that the special move wasn't over and Kirito grabbed hold of his sword that was flown threw the air and it was now in the colour of a blinding flame and Kirito slashed Silver Crow in a straight line.
There was an explosion which pushed Silver Crow to the back and to the right. Kirito looked up again and saw that the blow he received did about 15% of his health and he dealt Silver Crow about 30%. Kirito then looked at the rubble Silver Crow was in and tried to perform a sneak attack, however the rubble was scattered and Silver Crow wasn't in sight. Kirito found out that Silver Crow's stamina bar was now 30% and still decreasing, indicating that he was now using his special move. Kirito prepared himself for his front, back, sides and underneath however Silver Crow was in the air. Kirito realised that he had wings and tried to jump and get out of the way of the impact but Silver Crow moved with him and so he tried to defend from the sharp toe with his sword but it was impossible and got dive kicked into his shoulder. After the attack Silver Crow looked at Kirito's health and found out that it was just below 50% and into the yellow.
Before Kirito's right arm recovered, Silver Crow spread his wings again and rushed in again to swing a big roundhouse kick diagonally upwards however Kirito blocked it using his left hand and other sword, the Dark Repulser. Kirito used both swords to attack Silver Crow. Kirito checked Silver Crow's health and he had 40% remaining. Silver Crow then opened his wing waiting to counter-attack Kirito. Kirito seeing this, begins to charge at the speed of a bullet through a cannon and use Dual blades rush sword skill, «Double Circular». Kirito, infront of Silver Crow, rotated his body upward and used his black sword to slash upwards furiously damaging Silver Crow's left wrist armor, making a rip. Kirito then used his white sword to thrust into his neck. Silver Crow caught it by letting the sword penetrate his hand and catching Kirito's fist. Silver Crow then flew and during acceleration turned around and threw Kirito to the floor. Silver Crow did a long range roundhouse kick, hitting Kirito even through his block. Silver Crow rushed in again and Kirito blocked with both of his hands however Silver Crow violently headbutted Kirito's chest. Kirito then began to prepare for his special attack and Silver Crow rushed downwards while Kirito jumped to him. Both attacks pierced each other and Kirito disconnected.
In the end, Haruyuki was telling his story and said that the other one was stronger and he would've lost. Though with Kirito he talks with Suguha describing how Haruyuki's flying ability was different from ALO, where their flight wasn't true flight but rather just an imitation to what it could become, and that the fight ended in a draw.