After Kirito accepts the duel challenge of Heathcliff, a lot of players gathered on the 75th floor's city, «Collinia», in a Colloseum to watch the fight between the two highly-skilled players. Kirito is waiting in his room with Asuna, who is still annoyed that Kirito accepted to duel the strongest player in the whole game. Asuna reminds Kirito that Heathcliff was the famous player who was able to hold back a boss in a fight all by himself, plus the fact that no player had ever seen Heathcliff’s health bar reach the yellow zone. Kirito tells Asuna that he understands his odds, however he boldly declares that he still does not plan to lose easily.
Heathcliff VS Kirito.
While Asuna watches from one of the entrances, Kirito enters the arena to where Heathcliff is. After selecting the «First Strike» option for their duel, both Heathcliff and Kirito ready themselves as the timer counts down. When the timer reaches zero, Kirito starts out with full-on assault with his «Dual Blades», however Heathcliff is able to block all of Kirito’s attacks with his tower shield. Kirito seem to be at a disadvantage, as Heathcliff easily defends and attacks using his unique skill, «Holy Sword».
Kirito goes for the final blow.
Still not letting up on his assault, Kirito continues to attack with his two swords and finally knocks away Heathcliff’s shield to his side, creating an opening. As Kirito tries to goes in for the finishing blow, Heathcliff moves his shield at an impossible speed and once again blocks Kirito’s attack. Seizing the moment, Heathcliff makes a clean hit on Kirito causing his health bar to reach the yellow zone, therefore winning the «First-strike» duel.
On October 22, Kirito speaks with Asuna while readying for his duties in the Asuna confronting Kirito sadness.
guild and putting on a KoB uniform. In that moment, Asuna uses this time to question Kirito why he avoids guilds and excludes others, despite being a nice person. Kirito answers her about his time with the Black Cats of the Full Moon, and how they died because of him. Although shaken by the story, Asuna promises that she'll protect him, giving Kirito some relief for his guilt. In the Knights of the Blood HQ, Asuna talks to Godfree about taking Kirito to a mandatory training session in floor 55 to see his skills. Kirito accepts, and to his surprise, Kuradeel also accompanies them in their training. Before leaving, they give their crystals to Godfree as a method to prove their skills.
Kuradeel showing he's part of Laughing Coffin.
In the field on the 55th floor, they stop to rest and Godfree gives them each a portion of food. While drinking Kirito notices something weird, but it is too late, and both Godfree and Kirito are paralyzed by the poisoned water. Kuradeel stands and kills Godfree, revealing his revenge plan to Kirito and his membership in the PK guild, Laughing Coffin. He quickly finishes talking to kill Kirito before the poison's effect disappears, stabbing him repeatedly.
With his HP nearly depleted, Kirito is nearly at death's doors, but his desire to not leave Asuna gives him motivation to resist and hold back Kuradeel's blade for a second longer. Asuna, with tremendous speed, enters the scene just in time, blowing away Kuradeel and giving a healing crystal to the critically injured Kirito. In her fury, she relentlessly assaults Kuradeel who is no match for her speed. Just before the final blow, he surrenders and begs for forgiveness.
Asuna lowers her guard and Kuradeel uses the chance to attack. Kirito blocks just in time to stop Kuradeel by guarding a blow with his wrist, sacrificing his hand temporarily. Using his free hand, he kills Kuradeel with his Martial Arts skill «Embracer». Kuradeel's last words accused Kirito of being a murderer before shattering into polygons.
Kirito kissing Asuna.
After the harrowing experience, Asuna believes she is to blame for this and says that she will never bother Kirito again. Kirito stops her by kissing her, and embraces her, stating his life belongs to her. Not wanting to part ways from Asuna’s side, Kirito tells her that he wants to be with her for the night. They both later have dinner at Asuna’s house. Kirito is startled when Asuna suddenly rises from her chair at the conclusion of their meal, turns off the lights and starts to undress herself. When Asuna asks Kirito to take off his clothes as well, Kirito realizes the misunderstanding when he told Asuna that he wanted to be with her for the night. Kirito tries to explain the situation, however his apologies aren't enough and Asuna punches Kirito for the whole embarrassing ordeal.
Kirito proposes to Asuna.
Afterwards, Asuna wakes up to find Kirito recently out of her bed, happy that her time with Kirito hasn't been a dream. After hearing that Asuna plans to stay away from the frontlines for a while, Kirito brings up that there is a small village at the southwest region of the 22nd floor. Kirito asks Asuna if she will go there for a while with him asks her if she would marry him there. She then gracefully says yes.
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 Light Novel series, 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 original web-novel, Asuna didn't hesitate to kill Kuradeel when he began to beg for his life. In the Light Novel and Anime adaption, this was changed so that Kirito would save Asuna, after she had a moment of doubt, allowing Kuradeel to disarm, and attack her.
The scene with the "Ethics Code off" option was omitted from the anime.
It is heavily implied that Kirito and Asuna slept together. With Asuna waking up nude and clasping a blanket onto her body it can be assumed that they continued. This can also be seen in chapter 16.5 of volume 1 which only appeared on the web version of the light novel.
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