After Kirito accepted the duel challenge of Heathcliff, a lot of players gathered at the 75th Floor's main city, Collinia, in a Colosseum to watch the fight between the two highly-skilled players. Kirito was waiting in his room with Asuna, who was still annoyed that Kirito had accepted to duel the strongest player in the whole game. A terrified Asuna scolded Kirito for his actions and reminded him that Heathcliff was famous due to his Unique Skill, «Holy Sword», that granted him an outstanding offense and defense, plus the fact that no one had ever seen Heathcliff’s health bar reach the yellow zone. Kirito then told Asuna that he understood his odds, however he boldly declared that he still did not plan to lose easily.
While Asuna was watching from one of the entrances, Kirito entered the arena where Heathcliff was already waiting. After selecting the «First Strike» option for their duel, both Heathcliff and Kirito readied themselves as the timer counted down. When the timer reached zero, Kirito started out with full-on assault with his «Dual Blades», however Heathcliff was able to block all of Kirito’s attacks with his tower shield. Kirito seemed to be at a disadvantage, as Heathcliff easily defended and attacked using his Holy Sword.
Still not letting up on his assault, Kirito continued to attack by activating Starburst Stream and finally knocked Heathcliff’s shield to his side, creating an opening. As Kirito tried going in for the finishing blow, Heathcliff moved his shield at an impossible speed and once again blocked Kirito’s attack. Seizing the moment, Heathcliff made a clean hit on Kirito causing his health bar to reach the yellow zone, therefore winning the «First-strike» duel.
On October 22, at Agil's Item Shop, Kirito spoke with Asuna while getting ready for his duties in the Knights of the Blood guild and putting on the guild uniform, disliking it because of the colors. At that moment, Asuna used the opportunity to question Kirito why he avoids guilds and people, despite being a nice person. Kirito answered by telling her about his time with the Moonlit Black Cats, and how they died because of him. Although shaken by the story, Asuna hugged him and promised that she would protect him, giving Kirito some relief for his guilt.
At the Knights of the Blood guild headquarters, Godfree informed them about taking Kirito to a mandatory training session in the 55th Floor's Labyrinth to evaluate his skills. Although Asuna told Godfree that Kirito was stronger than him, Godfree made him go as Kirito had to comply with the guild's rules despite his relationship with Asuna. To Kirito's shock, Kuradeel also came to accompany them in their training, and because of now being Kirito's guildmate, apologized to him for his previous actions. Before leaving, they gave their crystals to Godfree as a method to prove their skills.
In the field on the 55th Floor, they stopped to rest and Godfree gave them each a portion of food, though Kirito was disappointed that he had been given a regular loaf of bread, instead of being able to enjoy Asuna's homemade food. While drinking, Kirito noticed something weird in Kuradeel's expression, but it was too late, and both Godfree and Kirito were paralyzed by the poisoned water. Kirito quickly told Godfree to use the crystal to cure himself, but Kuradeel kicked it out of his hand and subsequently killed him while enjoying Godfree's demise, turning into an orange player. As for the excuse he would make, he told Kirito that he would claim that the party was ambushed by orange players, and that he held them all on his own. After Kirito's remark about him being more suited for a PK guild, Kuradeel revealed his revenge plan to kill Kirito and his membership in the PK guild, Laughing Coffin.
With his HP nearly depleted, Kirito was nearly at death's doors, but his desire to not leave Asuna gave him motivation to resist and he struggled to remove Kuradeel's blade, though he was only able to hold it back for a few moments. Asuna, with tremendous speed, entered the scene just in time, blowing away Kuradeel, and then immediately used a healing crystal on the critically injured Kirito. She told Kirito that she noticed that something had gone wrong, as she was watching them from her map, and noticed that Godfree had disappeared. Knowing that it was highly unlikely for Godfree to be killed by monsters on this floor, as he stated that he would watching their skills, she rushed to the location. She then attacked Kuradeel, who tried to make an excuse saying that it had been a training accident, but then, after suffering numerous blows at godlike speed, he begged for mercy and told her that he would surrender and leave the guild.
At that point, feeling hesitation about killing Kuradeel, Asuna lowered her guard and Kuradeel used the chance to attack. Kirito blocked the attack just in time by taking the blow with his wrist, sacrificing his hand temporarily. Using his free hand, he then finished off Kuradeel with his Martial Arts skill «Embracer». Kuradeel's last words accused Kirito of being a murderer before he shattered into polygons.
After the harrowing experience, Asuna believed that she was to blame for the tragedy and said that she would never bother Kirito again. Kirito stopped her by kissing her, and embracing her, stating that his life now belonged to her. Not wanting to part ways from Asuna’s side, Kirito told her that he wanted to be with her for the night. They both later had dinner at Asuna’s house. Kirito was startled when Asuna suddenly rose from her chair at the conclusion of their meal, turned off the lights and started undressing herself. When Asuna asked Kirito to take off his clothes as well, Kirito realized the misunderstanding when he had told Asuna that he wanted to be with her for the night. Kirito tried to explain the situation, however his apologies were not enough and Asuna punched Kirito for the whole embarrassing ordeal.
Afterwards, Asuna woke up to find Kirito recently out of her bed, while happy that her time with Kirito had not been a dream. After hearing that Asuna planned to stay away from the front lines for a while, Kirito brought up the fact that there was a small village at the southwest region of the 22nd Floor. Kirito then asked Asuna if she would go there for a while with him asked her if she would marry him there. She gracefully accepted the proposal.
- Teleport Crystal - given by Kirito
- Antidote Crystal - given by Kuradeel
- Heal Crystal - given by Kuradeel
- Lambent Light
- Heal Crystal
- Aincrad Floor 55
- Aincrad Floor 75
- Collinia Arena
- Aincrad Floor 50
- Agil's Item Shop
- Aincrad Floor 61
- Asuna's house
- Adapted from Volume 1, Chapters 12, 13, 14, 15 and 16
- The scene where Asuna complains to Kirito for accepting Heathcliff's duel, in the Light Novel happened on the 50th Floor, in Agil's shop, while in the Anime, it happened right before the duel.
- In the novel, Kirito began the duel by initiating the Double Circular Sword Skill. In the anime, he did not start the duel with a Sword Skill at all.
- In the novel, both Kirito's and Heathcliff's HP had decreased to nearly 50% before Kirito used Starburst Stream, as Heathcliff started to look nervous. In the anime, Kirito did so after managing to scratch Heathcliff's cheek, while their HP bars look like the two barely received any damage at all.
- In the Light Novel, a group of four were part of the training session; while it was only Kirito, Godfree and Kuradeel, a group of three, in the anime.
- In the anime, Asuna healed Kirito immediately after repelling Kuradeel, while in the light novel, Asuna asked Kirito whether he was still alive before healing him.
- The scene with the "Moral Code Removal" option was omitted from the anime.