|Spoiler Alert: This article/section contains details about future plotlines described in the light novels, not covered in the anime. Do not proceed unless you want to be spoiled. |
Asuna is Kirito's partner and main love interest in the series. Among all the people Kirito has met, she is the closest and dearest to him. Originally the two of them only thought of clearing the game, but their relationship began when they partied on the 1st Floor. During the boss fight on the 1st Floor, he called Asuna by her name for the first time, noticing earlier her character name below the HP gauge. She was also one of the two people (the other being Agil) who knew the reason why Kirito branded himself a Beater. When the two parties meet again on the 74th Floor, Asuna normally cooks for Kirito. As the series progresses, the two of them fall in love with each other. After the two of them declared their love for each other, they are only concerned for the other's safety.
This led to the two characters getting married in-game where they resided on the 22nd Floor for two weeks as their honeymoon until being called back to the front lines. During those two weeks, Asuna reveals to Kirito and Nishida that in the beginning, she would cry due to the fact she was trapped in a death game and she would take that sadness and turn it into determination thus allowing her to level up extremely quickly. She explained to them that it was Kirito who taught her that there are people trying to experience this world for what it is and that he is the reason why she is alive and looks forward to tomorrow.
Their feelings for each other have created abstract situations. Their relationship is very serious, to the point that they cannot live on if one of them dies. An example is shown when Kirito asks Asuna not to take part in the boss fight in the 75th Floor to which she replies if he did not return, she will commit suicide thus joining him in the fight saying she will protect him Kirito when fighting with the final boss on the 75th Floor. As Heathcliff's sword comes crashing down at Kirito after the boss fight, Asuna, while still paralyzed, was able to jump in front of Kirito, taking the hit for him and costing her to lose her life in-game. Heathcliff announces that there is no programmed way to cure paralysis without a crystal or waiting for the paralysis to wear off. Also, because of Asuna fueling Kirito's determination when Kirito was stabbed by Heathcliff, he was able to successfully defeat Heathcliff by stabbing him in the chest after a message appears announcing Kirito was dead.
Kazuto/Kirito also does not give concern to his safety when it comes to rescuing Asuna. One example of this was when he tried to fly up the World Tree uncaring whether he fell and his avatar died or not. Kirito said that nothing would end and nothing would start until Asuna was released from the virtual world. After rescuing Asuna in ALfheim Online (ALO), the two of them finally met face to face and they officially became a couple in the real world.
Kazuto/Kirito tends to take things on to himself when it concerns Asuna, as shown in the Gun Gale Online (GGO) incident where he did not tell Asuna that there was a risk of him dying and took part in the mission in secret since he did not want to risk her safety. Asuna eventually found out the details on her own and rushes to Kazuto's side, holding his hand as he is fighting in GGO. Kazuto/Kirito said that it was her warmth that gave him the strength to win.
The two maintain a happy relationship even a year and a half after the SAO incident. Even though Kazuto had decided to go to school in America for the summer to pursue his mechatronics career, he asked Asuna to accompany him overseas, as he could not live without her, even if it was a very selfish desire. Asuna replied that her answer to that question was decided a long time ago.
In Underworld, Kirito still retained his memories and feelings for Asuna, but is unable to remember anything after the time he asked her to come to America with him. Upon realizing that he was trapped in the world, he was torn between finding a quick way to escape so that he could reunite with her and playing out his role in this new world.
Tsuboi Ryoutarou (Klein)
Klein is Kirito's first friend before meeting Asuna. He became Kirito's friend after he asked Kirito to teach him to play SAO. Klein was one of the few people that Kirito considered as a "friend". Klein really cares for his friends and is dedicated to keeping them all alive, which Kirito greatly respects. Klein tends to worry about Kirito, since he knows his loner nature, and tells Asuna to "take care of him" and that he "isn't a bad guy" to which she replies she will and she has long since known respectively.
Klein is also responsible for giving Kirito extra strength, as shown when Kirito was unable to revive Sachi because of the time of her death was too long for the Divine Stone of Returning Soul. He regularly meets with Kirito and his friends and occasionally go with them in quests in ALO, especially after the release of the World Seed. One such instance includes the quest for Excalibur.
Andrew Gilbert Mills (Agil)
Agil is an axe wielding merchant who has a good relationship with Kirito. He was one of the two people who knew the reason why Kirito became a Beater (the other being Asuna). Like Klein and Asuna, he also respects Kirito, and always offers any help he can when Kirito needs it (like sheltering him when Kirito became famous after his Dual Blades becomes known, or implementing the "Seed" that Kayaba gave Kirito). Agil is the first person that Kirito goes to when he wants to have someone examine any items he obtains from fighting or selling an item.
Outside of SAO, he is married and the owner of the Dicey Cafe where Kazuto and his friends often meet up for celebratory and important meetings (an example is the Aincrad Capture Commemorative Party or the Calibur quest afterparty).
Ayano Keiko (Silica)
Silica is a player that Kirito met when he was wandering around in the 35th Floor. When Silica asked him why is he being kind to her, he gave her a "manga-like" answer that she resembles his "sister". As they journey together, Silica begins to develop feelings for Kirito. After reviving Pina, she realized that she can't follow Kirito to the front lines due to her level (as she was level 45, and Kirito was 78), although she still is happy to be able to meet him and they keep in touch by adding each other as friends, something Asuna later noted as rare due to Kirito being an asocial solo player.
After the ALO incident, she goes to school with Kirito, Asuna, and Lisbeth. Both Silica and Lisbeth are in agreement to give both Kirito and Asuna space for one month before they make their individual moves on him. Though after seeing how close Asuna has gotten to Kirito (made him lunch at the time) they quickly regret their "pact".
Shinozaki Rika (Lisbeth)
Lisbeth, a close friend of Asuna, was approached by Kirito for her blacksmithing skills (a referral from Asuna). Kirito requested a custom sword, and after he broke the best sword she had in stock, she forced him to accompany her in a quest to find the special ore required for the job. During the quest, due to his actions and his unexpected kindness and virtues, she develops feelings for Kirito. After the quest, she requests to become Kirito's personal blacksmith, hinting a romantic nature (which Kirito immediately realizes). She is devastated when she finds out that Kirito is Asuna's crush and there are mutual feelings between the two. Though her feelings were unrequited, she finds solace when Kirito tells her about the "Black Cats" and admits, for the first time after losing his guild, he had felt alive again when he was partying with her.
Despite initially giving Kirito to Asuna when the game is cleared, she knows right away that Kirito is the one who did it and among all the cheers she shouts out at the top of her lungs that she loves Kirito and that she swears they will meet up in the real world. Right after they meet in the real world, she becomes a regular player in ALO and frequently takes on quests with Kirito and his friends and takes up tasks of upgrading their equipment. She also goes to school with Kirito, Asuna, and Silica.
Sachi was a member of the guild Moonlit Black Cats who Kirito befriended. They became very close, to the point of sleeping together in the same room; their relationship described as "two stray cats licking each other's wounds" as they comforted each other. Their relationship was close enough that they had a shared page in each other's inventory (similar, but not quite at the level of married players who had combined inventories). Kirito promised her that she would not die, though unfortunately, he would not be able to keep his word. Even after her last message gave him the strength to live, he still never fully was able to escape his guilt until he married Asuna.
In the web version of SAO1 written back in 2002, Kirito told Asuna they have had a private relationship and in a 2005 Q&A activity, Sachi was revealed to have been Kirito's first love within the canon of the Web Novel. However, as of 2006, there are barely any trace of these in the web novel version of Red-Nosed Reindeer, in which Kirito denied the existence of any form of romantic relationship between him and Sachi. Additionally, in the published version of the story, the parts describing their relationship were edited, once and for all making the web novel's version of their relationship no longer viable and thus Sachi is no longer treated as Kirito's first love in the canon of published version.
Yui is Kirito and Asuna's in-game daughter who is an «Artificial Intelligence» (AI). While Kirito loves Asuna as his fiancé/wife, Kirito loves Yui as his own daughter and Yui in turn thinks of Kirito and Asuna as her parents. In the real world, Kirito uses his skills and resources to make a device for Yui to view the real world even whilst she is in virtual reality and gives her the ability to communicate with them.
Yui is one of Kirito's most beloved people. In ALO, she takes the form of a navigation fairy who is always seen on either Kirito or Asuna's shoulder, or napping inside Kirito's breast pocket. Yui tends to misunderstand why humans aren't direct in expressing their feelings, saying if she was the one who did it then she would simply be forward about it (she then kisses Kirito on the cheek). She also gets annoyed when any girl other than Asuna, Leafa, Sinon, or any of their friends from SAO interacts with her "Papa".
When in ALO, Kirito trusts her with sensory duty, given her AI affinity for it. He tends to show affection to her pixie form by playfully poking her head, which she finds a little annoying. He is very much a doting father, making sure she stays safe during a battle and doing whatever he can to make her comfortable. Though Yui loves Kirito dearly, she has disapproved of a few of his shenanigans, like biting Leafa, and scolds his "bad behavior".
Yui finds great delight in watching Kirito battle, showing unrestrained glee at his ultraviolence while other members of the party are more concerned about the battle.
Kayaba Akihiko (Heathcliff)
Kirito mentioned in the beginning of the series that Kayaba Akihiko was his hero, and he looked up to him. When Sword Art Online became a "Death Game", Akihiko became his enemy. Akihiko is indirectly responsible for numerous tragedies around Kirito, as it was because of him that the players who would die in the game would die in real life as well. Nonetheless, Kirito and Akihiko are shown to have mutual respect for each other.
Pina has a strange attraction to Kirito, as Pina is said to fly off of Silica's shoulder and curl up on Kirito whenever she came across him sleeping. Even when Kirito is not sleeping, Pina is still attracted to him, like when Silica invited Kirito to a restaurant to celebrate her birthday, Pina became interested in Kirito's tart, even though Tamed Monsters are only supposed to be interested in food when fed by their tamer, and then curled up on his head.
Kirigaya Suguha (Leafa)
Kirigaya Suguha is Kirito's real life adopted-sister/maternal cousin. Kazuto created distance between them when he found out they weren't real siblings but instead cousins. After clearing SAO, this becomes something he regrets as he tries to reforge their relationship. When Kirito was trapped in SAO, Suguha was conflicted with her feelings for Kirito and eventually realized she loved him. She originally joined ALO, using the alter-ego name Leafa in an attempt to better understand him. She becomes depressed when Kazuto visits Asuna on a consistent basis, realising where his feelings lie.
She unknowingly met Kazuto under his screen-name Kirito while he was trying to save Asuna in the World Tree. She eventually developed feelings for him without knowing Kirito was really Kazuto and was distraught when she found out his identity. After helping him rescue Asuna, she had come to deal with her feelings and instead acted as a supportive sibling towards her cousin, similar to their original relationship.
Asada Shino (Sinon)
When Kirito first logged into Gun Gale Online, he soon became lost and attempted to ask the first person he met for directions. Due to his new avatar being shorter than his spriggan avatar, Kirito did not realise that Sinon, the first person he encountered, was a girl until he had already attracted her attention. Kirito pondered how to act in this situation, fearing that Sinon would think that he was trying to flirt with her, but when he realised that Sinon had mistaken him for a girl, he decided to use this misunderstanding to his advantage.
Kirito quickly gained respect from Sinon the instant he tackled an extremely difficult arcade game and won on the first try. However, when he inadvertently saw Sinon changing her equipment in preparation for the Bullet of Bullets preliminaries, he finally decided to inform Sinon that she had mistaken his gender. The circumstances caused a rift to form between them, transforming Sinon's early amicability to a heated sense of rivalry.
On the other hand, Kirito tried to remain friendly to her throughout. He also acknowledged Sinon's sniping abilities, believing that she was a dangerous sniper, and valued her experience in Gun Gale Online, such as when he relied on her input when they formed a team to defeat Death Gun during the main Bullet of Bullets tournament.
The rift in their relationship was gradually mended over the course of the tournament, especially after Kirito and Sinon shared their mutual traumatic experiences of having killed another person with one another. In the aftermath of the Death Gun incident, Kazuto, with the help of Asuna and Rika, arranged for Shino to meet Oosawa Sachie, the young mother Shino had saved during the post office incident, and her daughter Mizue, helping Shino tremendously in overcoming the guilt that had burdened her for years.
A couple of weeks later, Kirito invited Sinon to join them on a quest to find the Holy Sword Excalibur in ALfheim Online. On the way there, he jokingly grabbed her tail in response to one of her quips, thus angering her. When Sinon later retrieved Excalibur as it was falling towards the Great Void, she decided to return the favor by teasing Kirito that she would return it to him on the condition that he thought about her every time he used it.
Alice is one of Kirito's friends during his first dive.
Sortiliena is Kirito's senior in the Sword Mastery Academy, whom he acts as a valet for. The two mostly had a relationship strictly platonic between a valet and an Elite Swordswoman, though he personally grew special flowers to give to his mentor.
Ronye acts as Kirito's valet during his second year in the Sword Mastery Academy.
Cardinal wanted Kirito to facilitate her plan of defeating Quinella and then cease the existence of Underworld before the Load Experimental phase could take place. She secretly followed and guided Kirito's actions via Charlotte for more than two years to do so. Although Kirito does not agree with the plan, he still decided to help with the first part of her plan. In addition, Kirito gave Cardinal a warm hug under her request, to which she exclaimed that she finally experienced what it meant to be a human and that she had finally been rewarded for her two hundred years of work.
Although Charlotte was originally indifferent to observing Kirito and Eugeo according to Cardinal's command, as, in appearance and verbalism, they were not much different from those of the same area and age. However, throughout her months of observing them, Charlotte became influenced by them and emerged a sense of emotion in helping them complete their mission, despite not being given such orders, thus she secretly helped them throughout their trip.
Selka is the one who was taking care of Kirito when he came to Rulid Village during his second FullDive into Underworld. Before they parted ways, Kirito kissed Selka's forehead and promised to bring Alice back to the village as a test to confirm if he was an artificial Fluctlight or not.
Nurse Aki is a nurse who Kirito was acquainted with. She took care of Kirito previously during his long rehabilitation. She watched over Kirito when he was going to investigate the Death Gun incident. Outside his friends from SAO, she learned about Kirito's dark secret, "the fact that he killed three players from SAO." After that, she encouraged Kirito that he had done the right thing, stating that "a minority has to be sacrificed to save the majority." She appears to have respect for Kirito's maturity in handling his guilt and as he enters GGO calls him a "Hero."
Kikuoka Seijirou is an investigator in the «SAO Case Victims Rescue Force» who Kirito was acquainted with. He has taken a personal interest in Kirito's abilities, thus uses the GGO incident to forge a relationship with him. Kirito does not trust him at all, since he never reveals the full truth, going so far as to tail him to another meeting. Kirito still feels grateful to him since he was the first one by Kirito when he woke up from SAO and was also the one who told him where Asuna and the others were located. Kirito seems to not hold Kikuoka in high regard, for multiple reasons such as his career as a bureaucrat, and suspicions of him having ulterior motives. Kirito even uses casual speech when addressing him, which would normally be considered very rude in Japanese culture. That said, Kirito has claimed to see him as highly skilled, and very competent; and not someone to be taken lightly.
Kirito heard of the name Absolute Sword in the New ALO and had a fight with her when Yuuki was challenging others to street fights to find a player strong enough to challenge Floor Boss of New Aincrad to leave every one of her team members' names on the Monument of Swordsmen before her death. Although Kirito was a worthy opponent, he was defeated when he let his guard down to remark that Yuuki was living in the virtual world, thus Yuuki thought that Kirito could not help her to achieve their goal due to discovering that Yuuki was a Medicuboid user, even though his sword skills were strong enough. Sometime later, after Asuna met Yuuki in hospital, Kazuto managed to construct a system for her to let Yuuki go to school, among other places, like her old home. During that time, Yuuki visited the Kirigaya residence, and become good friends with Kazuto.
Midori is Kazuto's aunt and Suguha's mother. She became his guardian after the death of his parents and raised him as her own son, even hiding the fate of his real parents. However, Kazuto later discovered by himself that she was not his real mother, but even so, he still treated her the same.
In other stories
Kirito meets the Silver Crow while testing a 4th generation FullDive device, the Soul Translator. Instead of appearing in peaceful grassland as expected, Kirito finds himself in a post-apocalyptic world where he sees what seemingly looks like a robot. Although Kirito attempts to make contact with the entity, apparently called Silver Crow, the other party is apparently unable to hear him. Kirito then carelessly makes a step while still holding onto his sword, thus provoking the panicking Silver Crow to attack him. After the battle ended with a draw, back in the real world, Kazuto admits that he has dueled an amazing opponent.