In Volume 2/Episode 3 "Red-nosed Reindeer", Kirito intends to solo a level boss to get a resurrection item to revive the dead Sachi, but is slipping deeper into a Death Seeker phase. Klein shows up, with the rest of his guild in tow, and begs Kirito to party with them and challenge the boss together, because Klein is afraid he'll die if he tries to solo the boss. When a PK-happy guild shows up, 30 men strong, Klein leads Furinkazan's 10 man guild to Hold the Line and give Kirito a chance to beat the boss.
After the boss is defeated, and Kirito learns the resurrection item won't work for Sachi, he gives it to Klein.
After that, during the Christmas of the first year in Sword Art Online, Sachi's recorded message for Kirito - obviously pulls double-duty as a Tearjerker. While Kirito's still heartbroken over her death, the light novel implies that hearing the message kept him from becoming a Death Seeker.
The entire chapter/episode focusing on Kirito helping Silica revive her pet dragon Pina is just filled to the brim with this.
Kirito talks about his sister and how he'd been so aloof towards her once he found out they're not biological siblings and feels so bad for ignoring her. Silica tells him that she's sure that his sister still loves him anyway which ends up making him smile.
In Volume 1/Episode 9, when Klein asks Asuna to take care of Kirito. It's played for laughs in the LN, but is heartwarming in the anime.
Chapter 19, when we finally get to see the story behind Asuna and her actions with Kirito, and damn, isn't it full of fluff from their accidental meeting to their in-game marriage.
Agil's wife kept his cafe running, and waited patiently for him to come back to her. He did.
The last parts of Chapter 15 and up until 16.
For the anime, the end of Episode 10 where Kirito asks Asuna to marry him is chock full of this, and has a very powerful When She Smiles moment.
Asuna explaining to the fisherman they befriended just how much meeting Kirito had helped her.
Asuna: When I began to think about Kirito-kun whenever I would fall asleep, the nightmares stopped.
Episode 14, which doubles as tear jerker. Kirito and Asuna finally tell each other their real names. Kirito then says this is goodbye, however Asuna tells him he's wrong, as they would be together until the very moment they disappear so they would forever be together. And when Kirito wakes up in the hospital, weak from two years on life support, he immediately gets up to find Asuna.
Fairy Dance Arc
Once Kirito enters into ALO he checks his inventory to make sure a very special item is still there. When he selects it Yui appears and he embraces his daughter tightly in their first reunion since SAO.
Volume 4's denouement. Kirito and Leafa dancing together in the sky, and coming to terms with their emotional baggage.
The Sylphs and Cait Siths' Big Damn Heroes moment is this for multiple reasons. First, it's Kirito's Karmic Jackpot for staying loyal to Leafa and saving the Sylph-Cait Sith alliance, even though it would have seemed to be more in his benefit to betray her and join the Salamanders. Second, Sakuya and Alicia Rue know that a failure will bankrupt their races and result in both of them losing their positions as leaders of their races. Third, since only one race can get to the top of the World Tree and earn flight (or at least that was assumed to be the case, since no one was meant to get up there), the two races aren't acting in order to advance their own interests. Fourth, there's Leafa's reaction, especially considering how her obligations to Sigurd's group and growing disillusionment with guild politics had sapped her enthusiasm for ALO.
"Thank you...Thank you both," Leafa said, her voice trembling. There really are more things in this world more important than rules and manners, she told herself, heart soaring. There was nothing more to say.
Episode 23: after finding out who Kirito is, Leafa challenges him to a sword fight. In the middle of the fight, she throws a fight, but he did the same as well. Then, they hugged each other and apologize for keeping their true identities a secret from one another.
Episode 24: Kirito and Yui finally reach Asuna's cage; hugs and tears all around. After Sugou's dealt with, Asuna and Kirito embrace once again; she calls him her hero and while he says he's not one, he'll try for her sake. Asuna logs out and hopes that Kirito will be the first thing she sees when she wakes up. When Yui returns, (having been banished by Sugou) she hugs her papa and then asks if her mama is okay. Even Kayaba contributes by giving Kirito a Heroic Second Wind and a I Was Just Passing Through excuse.
The last twenty or so minutes of Episode 25, so much. Kirito and Asuna finally meet in real life. Asuna's hearing is off because of her prolonged dive, but she understands what Kirito is trying to say. Outside the hospital window, representations of Kirito and Asuna's SAO avatars can be seen holding hands and then walking off. The next scene sees them in school, eating a lunch Asuna made, then sharing in minor PDA. The screen pans out to Lizbeth and Silica with their I Want My Beloved to Be Happy. THEN there's a party for the survivors of SAO that celebrates Kirito clearing the game. Back inside Alfheim, Leafa shows Kirito how to dance inside the game and then everyone (Asuna included, who is now an Undine) flies toward the reborn Aincrad.
Also making an appearance are Thinker and Yulier, who have married.
A small but meaningful detail: In Episode 1 of the anime, there's a scene of a G.I.R.L. and a young looking man revealed to be a skinny man and a stout somewhat older man when Kayaba resets all the player avatars to reflect their true real-world selves. A few episodes later, they're seen talking together. At the end of the Aincrad arc, there's a brief scene in a hospital where these two men reunite in the real world with much happiness, to the surprise of the hospital staff. Whether or not this included a Relationship Upgrade at any point is never addressed.
Once the ALfeim arc is finished, the extra addition follows the SAO crew going on an underwater quest so Yui can see whales. It's very touching the lengths they're willing to go in order to give the little girl a fun experience.
Phantom Bullet Arc
Episode 7, Season 2: Kirito is telling his nurse Aki about how he killed three people in SAO and only now feels the guilt for it due to having encountered one of the survivors of the group they were part of. What follows is Aki reassuring Kirito that he did the right thing and that he deserves to move on from the guilt.
Episode 13, Season 2: Sinon giving Kirito a big hug as she blows them both up with a grenade. Just look how happy she seems as she embraces Kirito. Coming after everything that's happened, it really feels like everything will be alright ...until Kyouji tries to kill Shino.
The ending of the Phantom Bullet arc:
Shino asking Kikuoka if she can visit Kyouji. In spite of everything he's done, from killing multiple different people to trying to force himself and a Murder-Suicide on her, she still sees him as a friend and wants to help in saving him as a person instead of leaving him to suffer in isolation.
Kirito meets with Sinon in the real world and brings her to Agil's bar (after a meeting with Kikuoka). There she meets Asuna and Lisbeth whom Kirito told about Sinon's past, so they could track down the bank teller whom the robber was threatening that day. It turns out, she was pregnant at the time and she and her then-unborn daughter wouldn't have lived if it weren't for Sinon doing what she did that day. The clincher is the picture that Mizue (the daughter) gives to her.
Shino onee-san, thank you for saving mama and Mizue
While this is already heartwarming enough, episode 14 of SAO II makes it even more heartwarming.
Caliber Epilogue: Kirito builds a system to let Yui interface with Agil's bar.
Mother's Rosario Arc
Episode 18, Season 2: The girls are all at that little house on Floor 22, at a sorta-sleepover, and a few of them are feeling sleepy. Why? Because of the adorable sight of Yui, cozily sleeping on the resting Pina, who is also resting on the asleep Kirito.
Then, in the flashback, the family's absolute tearful joy at finally getting their house back. Asuna said that it felt more like home than her one in the real world.
When they arrive at the purchase panel for the home, Navi-Pixie Yui flies out of Kirito's pocket and off-screen behind them; there's a flash of light, and then she drops down in her child mode and hugs them both from behind. The sight is enough to make a grown man squee.
There's also the boss fight that unlocked Floor 22. The old Aincrad gang (Agil, Klein, Lisbeth, and Silica) plus Leafa and Sinon all show up to help Kirito and Asuna beat the boss. Even Chrysheight (aka Kikuoka) is part of the raid.
In Volume 7, overlapping with Awesome: Kirito and Klein arrive to Hold the Line against a rival guild, so that the Sleeping Knights and Asuna can challenge the level boss.
Before Asuna duels with Yuuki, Liz notes that Kirito wasn't Dual Wielding when he fought, and takes that as a key indicator that he doesn't fight seriously unless it's no longer just a game. An episode or two later, the Sleeping Knights go for their second attempt at the floor boss and they get stopped by the raid squad - a couple dozen are guarding the doors, and a couple hundred coming up from behind. Kirito comes out of nowhere to stop the crowd, and when Asuna gets the Sleeping Knights to deal with the vanguard, Kirito puts on a second sword. And not just "a second sword", but frickin' Excalibur. This is beforeThe Reveal that the Sleeping Knights are all terminally ill and Yuuki is a Medicuboid user, so for all Kirito knows, it is still just a game, which means that he's getting serious for the express purpose of letting his girlfriend and her new friends do what they're trying to do. Love at its finest.
Another way to look at it however? When Asuna asks why Yuuki didn't pick Kirito to help them despite being as strong of a player, Yuuki says it's because he found out her secret. Maybe it wasn't just a game to Kirito, but considering he realized Yuuki's secret, he likely realized the Sleeping Knights' reason for getting their names on the Monument of Swordsman actually was more than just a game to them. That means even though he barely knows the Knights, because Asuna wants to help them, he's following his usual rule for when he gets serious even for their sakes because this moment's more than a game for them.
Episode 23 is literally nothing but these. First, by using a setup similar to the one that allowed Yui to interface with Agil's bar, Asuna essentially brings Yuuki to school with her. What really takes the cake is how all of her teachers and classmates don't even bat an eye at this, and welcome her with open arms. Then, Asuna takes Yuuki to the home she used to live in, as she wanted to see it one last time before she died. The day ends on a bittersweet note; Yuuki thanks Asuna from the bottom of her heart for the wonderful experience, but it becomes increasingly clear that she doesn't have much time left. However, that's not all that happens. Encouraged by Yuuki's words, Asuna finally wins her mother over, by taking her inside the game and showing her some scenery that brought back some memories of her parents' home. After the fact, while she still seems to have her cold exterior, she decides to allow Asuna to continue going to the school she's currently attending, as opposed to forcing her to transfer as she initially intended.
Her mother, who was so icy and strict about everything and tried to keep a professional and distant attitude even with her own daughter at all times, breaks down into tears from the pleasant memories of her parents thanks to Asuna, who doesn't even hesitate to comfort her despite resenting how she's treated her.
In Volume 7, Ill Girl Yuuki logs into ALO one last time as she's dying, to say goodbye to her friends. And then the leaders of the main factions of ALO perform a fly-past with their members. Over ONE THOUSAND ALO players from different factions put aside their differences to give her a send off. This even includes the Jerkass players who'd spied on her guild attempting the floor bosses, and later tried to bar her way, perhaps showing that they'd come to respect her.
Beyond that about two hundred players come to her real world funeral, surprising her remaining family who thought she had no friends.
Episode 24 comes the most Tear Jerker and heartwarming moment of the entire Season 2 where thousands of SAO players pays their respect bidding Yuuki farewell after Yuuki logs into the Medicuboid one last time. It was very heartwarming that viewers would break into tears after her long battle against AIDS.
The episode also skips the opening for a montage of Asuna and Yuuki spending their days together making it all the more heartwrenching when Asuna learns that she's dying.
A moment that's Heartwarming in Hindsight, but the fact that Siune, who's ethnically Korean, is able to find acceptance in the Sleeping Knights, and also befriends Asuna during the latter's time in the guild. Considering how tensions between Korea and Japan are a problem in the Alicization arc, as they are in real life, it's touching to see people look past their differences and bond over a game.
The Sleeping Knights are featured on "MMO Tomorrow" and it's revealed the remaining members didn't disband their guild as they had originally planned. They are still happily playing ALO together even though Yuuki is no longer with them.
After Asuna is forcibly stripped of the memories of the two years she spent in Aincrad, and is stricken by the grief of losing the precious moments where she met Kirito and Yui, the latter two huddle together with their wife and mother in a warm embrace, assuring her that memories or not, their love for her will remain. Though often snarked by mean-spirited hatedom as glorified "playing house", it is moments like this that prove the Kirigaya Household is truly a family.
Kirito discovering Asuna's scheduler she uses to remind her of the promise with him. He proceeds to give her a tackle... hug and promises her that he'll get her memories back.
Yuuki may have passed away months ago but even that does not stop her spirit returning from Heaven to guide Asuna's hand as she executes a devastating Mother's Rosario that defeats the True Final Boss of Aincrad Level 100 and saves a stadium of innocent SAO survivors and concertgoers. Friendship and Love truly does transcend Death.
Yuuki's spirit also takes the form of her avatar meaning she gets to spend eternity, not as the bedridden Ill Girl she was in life but as the friendly badass warrior everyone fell in love with.
Yuna got to fulfill her dream of performing live on front of a concert, with a truly emotional song that doubles as being a farewell.
The ending where Kazuto and Asuna fulfill their promise from Aincrad to go to a certain mountain and star-gaze. It ends with him officially giving her a real ring. They're engaged in real-life now.
The in-story book about SAO survivors originally ignored many lesser-known players, including Eiji (as Nautilus) and Yuuna. In the epilogue, the book is reprinted with additional tribute to these players.
Kazuto notices Shino no longer has phobic attacks from making a finger gun, meaning she has almost completely recovered. She also reveals she is still visiting Shinkawa who has greatly stabilised.
Asuna and Suguha have apparently joined forces to make sure that Kazuto eats properly.
Asuna has an app on her phone that measures Kazuto's heartbeat (long story), and he teases her about checking it when she has a spare moment. She says it relaxes her. Adding to the heartwarming, Kazuto is so comfortable with her having data like this that he created the app himself.
Since the Phantom Bullet arc, Shino's made a few friends and has become fairly close with Asuna, who invited Shino over to her house and gave her the Affectionate Nickname of "Sinonon." It's a clear sign of how much Shino has changed, as well as a welcome change from having virtually no friends.
Kazuto says that he's planning to go a college in America that's working on next-gen full dive technology and asks Asuna to come with him. He's nervous about it but she treats it like Ask a Stupid Question...; of course she'll go with him.
Kirito and Eugeo marching into the North Cave to look for Selka. When they find out that she has been captured by a band of thirty goblins, they don't hesitate to rescue her despite the fact that they are outnumbered, unarmed, Eugeo has no fighting experience and Kirito only has virtual experience from a game. Kirito sees it as his responsibility to save her because it's his fault she's in trouble and Euego has a Failure Knight thing he's working through.
We get this from Eugeo: when he leaps to Kirito's aid and saves his life. "Whe-When we were young we promised me, Kirito and Alice, from the day we were born together, to the time we die together this time, I must definitely protect I must "
When trying to save Eugeo's life, Kirito wonders if Rath is intentionally allowing the residents of Underworld to suffer, and would rather see Kirito fail to save Eugeo.
After Eugeo sees Kirito has mastered the Sword of Blue Rose and uses it to activate a Sword Skill and make a gigantic cut in the Gigas Cedar. Eugeo request Kirito to teach him how to use the sword, desiring to become stronger so that he will never make the same mistake as he did when he let Alice get taken. Kirito heartfully agrees to teach Eugeo everything he knows. We get to see a Training Montage where Eugeo learns to use the sword and the Gigas Cedar's Durability rapidly wears down.
In order to confirm that he is truly himself and not a fluctlight clone, Kirito decides that he has to use a personal counterpart to the world's Taboo Index. If he defies something so intrinsic and personal, that will prove he is the real him. What does he choose? kissing Selka's forehead. He makes a silent apology to Asuna and Yui before hand.
In Episode 5,
In the novels, only Asuna, Shino, Suguha and Yui worked on the Case of the Missing Kazuto. Here, Rika and Keiko join in the deduction phase and Ryōtarō helps out by driving the group. It is all the more heartwarming to see all of his friends banding together.
In the novels, When Kikuoka incredulously asks Asuna "How did you get through the University firewall, much less hack the student database?" To which Asuna proudly answers "My Daughter happens to be an expert at getting through firewalls." Even in the physical-world, Asuna's love and regard of Yui as her real child is now all-but undeniable.
In Episode 6, Asuna hears Rinko's story- because she couldn't bring herself to kill Kayaba, she blames herself for so many SAO players dying, and told this to Asuna as an apology of sorts. Asuna doesn't judge Rinko, saying that because she fondly remembers the time she spent in SAO with Kirito, she believes she's partly to blame, too, and that even if they can't be forgiven, they can simply move forward.
Episode 12 features an adorable moment with Cardinal. While stoically explaining the situation to Kirito, she bashfully states that she has one other desire than stabilizing the system. It's a hug. Suddenly she becomes the little girl she resembles. She hugs him like a girl would a teddy bear. Recognizing how lonely she must have been, Kirito embraces her. She then states the hug was worth waiting two hundred years.
Episode 19, Alice finally stops resisting Kirito and listens to him explaining her past life prior to becoming an Integrity Knight, of how she was born and raise in Rulid Village and had a younger sister named Selka. Even though Alice can't remember, the name Selka does feel familiar to her and for the first time she sheds tears and smiles. Alice looks up at the night sky thinking of Selka, while far away Selka herself is doing the same thing.
While Alice is forbidden from re-entering her village, by her own father, no less, and most of the villagers use her to do odd jobs they can't do themselves, there is one person who accepts her- her younger sister, Selka. Seeing Alice act as a Cool Big Sis to Selka brings out a warmer side of her personality that she doesn't show around many people.
In Alicization Invading, Alice meets Ronye and Teise again, and learns that the girls still blame themselves for what happened to Kirito. Alice then comforts them, saying they aren't at fault, then shares a little about herself, such as accepting that Alice Zuberg is a part of herself.
Among the combatants who fight in the War of the Underworld are the surviving Sleeping Knights, proving that whatever their illnesses may be, all of Yuuki's friends are alive and well.
Right before he dies, Bercouli has the chance to show his fatherly love to Alice:
"In the end, you were my only disciple, and my daughter."
He also meets a vision of Quinella, made from his memories of her. When she asks if he holds it against her for stealing his memories over and over, he replies that he doesn't, because despite everything he lived a thrilling life until the very end.
Speaking of the above, Kirito doesn't give in to PoH's goading him to kill the players who'd been manipulated into fighting against his friends. As the life energy of those players refuses to return to PoH's Mate Chopper, Yuuki's spirit tells Asuna the following.
Yuuki: You said it, remember? Life is a tool that transports and relates the heart. All these people from different countries who gathered in this place? They dont really want to kill one another. Everyone has the same wish. To go to a world of excitement and fun A great, beautiful, thrilling world like the land of fairies where you and I met, Asuna Thats all there is to it.
After all the crap Kirito has been through since his first day in gaming, he gets a warm "welcome back" greeting from everyone upon his arrival for the ALO conference. Even his adopted parents are aware that he's the famed "Black Swordsman"; someone else wrote a book about Kirito's adventures in SAO and they read it.
Even before that, when Kirito and Asuna logged into ALO, Yui tackles the former while nuzzling his cheek like a kitten. So cute~!
While Kazuto is still mourning over Eugeo's death in his room, Suguha comes in to comfort him. Then Kazuto tells her about his experiences in UW. Dude really misses Eugeo, huh?
Suguha/Leafa entered SAO because she missed her brother, being no longer able to stand by watching helpless and not knowing how Kazuto was doing, and sought to help him clear the game. Sisterly love at its finest.
Beating the Hollow Area story means Philia can rejoin the players on floor 76+.
In the Hollow Area, Kirito encounters a Hollow Data version of Sachi. She has Identity Amnesia and can only remember that she needs to fight for some reason. A very reluctant Kirito lets her go through with it, but is determined to stay by her side and protect her to the very end, and he succeeds this time. Sachi then remembers everything, that she's not the real Sachi. She also remembers what the real Sachi was going to say to Kirito, that Kirito never got to hear. Sachi tells Kirito that she knew she was a coward and was timid, leading Kirito to want to protect her. Sachi explains in that final fight she was terrified and wanted to run, but she stayed and fought, which was when the real Sachi also bravened up and it was all thanks to Kirito inspiring her. She ends it all by thanking Kirito for everything, having told him what the real Sachi would have, even though a tearful Kirito doesn't feel he deserves any thanks. Hollow Sachi then reveals she will always be in the Hollow Area waiting if Kirito ever feels the need to see her.
Re: Hollow Fragment adds a new side quest once you reach Floor 99, what makes this new quest heartwarming? You can actually rescue Strea, allowing you to partner with her on Floor 100. The scene where she reunites with all her friends when she returns to Arc Sophia is just beautiful.
Just the simple fact that Kirito and the rest of the gang can just hang out and play a game together without the fear of dying, seeing as in this timeline they were in SAO for even longer than usual.
Seeing Strea happily play with the rest of the party is this considering what happens to her in the climax of the previous game. She's alive and is no longer alone, surrounded by people who care about her and she cares about. Even in the amusing side stories where she makes outfits for the female members of the party, the only thing she cares about is seeing her friends' smiles.
The retelling of the Mother's Rosario arc is just as heartwarming as it is in the light novel and anime, except this time there's one more silver lining: Yuuki's condition improves, meaning that she'll be able to stay with her new friends in the long run. Yes, Yuuki survives in this route.
The scene where Rain and Seven, two estranged sisters, reunite for the first time in years. Then they later perform a duet together at one of Seven's concerts.
During Lost Song certain conversations can be triggered between active party members. These can range from funny to heartwarming. Of particular note is one between Kirito and Asuna where they express joy at playing ALO together and compliment each other. 
Sinon: This idiot right here, with his careless smile and his kind laugh and his constant miracles... You can always depend on him. He is stronger than anyone I've ever met, despite his irrational streak. He has saved me dozens of times. So yes, Premiere, you can trust him. Moreover, you should.
The simple fact that Yuuki is in this game, alive and well. In a contrast to her fate in canon, we get to experience firsthand what life could have been like if she survived the events of Mother's Rosario. Yuuki retains her trademark optimism and swordsmanship but is no longer held back by her disease and can freely interact and play games with the rest of the cast like a normal girl. She may not be able to meet the gang in real life just yet, but that doesn't stop her from enjoying her new life to the fullest and taking things easy at the same time. After an entire life's worth of fighting AIDS, Yuuki seems to have finally found her own inner peace.
If you look carefully at Yuuki's lines when she first appears in-game, you'll notice that she says she had to go to the hospital as part of why she couldn't play the other day. Although she's still restricted to get clean room, she's happy that she gets to stick around for far longer than she had originally expected.
In canon, Yuuki was seen attending school thanks to Kirito's VR probe. But in Hollow Realizations she's actively taking classes and learning, being happily tutored by Asuna-sensei. To show her gratitude, Yuuki (and Strea) make a bouquet of flowers for Asuna (which took many attempts to perfect), to which Asuna treasures forever. After Yuuki's first test she gets her grades back, and she's delighted to see she got top marks! You go girl!
Philia's pillow talk is pretty heartwarming. She reveals that while she was trapped in the Hollow Area it's meeting Kirito that gave her hope to continue surviving and that he was like her knight in shining armor coming to her rescue. Shortly after they start talking about Philia's treasure hunting, to which Philia says her treasure hunting sense was going off right in Kirito's room. Kirito becomes confused as the only valuable things in his room were swords which he didn't think counted as treasure. Philia tells him the valuable treasure is right in front of her, grabs Kirito's hand, and says:
Philia: Isn't it obvious? You. You are my greatest treasure. Kirito: Me? I don't think you'd get much for me on the open market though. Philia: I would never want to sell this treasure, it has had such an impact on my life, made me hope, made my future bright and clear. This is one treasure I never, ever plan on letting go.
Sinon confessing her Dark and Troubled Past (identical to canon where she shot a bank robber at the age of eleven) to her friends, feeling guilty for having lied to them and believing they would no longer accept her since she's a murderer. To her surprise, none of her friends think any differently of her as a person and wish to help her carry the burden she's lived with for so long. A tearful Sinon thanks then for being her bestfriends.
Accel World VS Sword Art Online
While thinking about the future of the Accel World time period, Yuuki is certain she won't be around to see it, as her surviving until now was already a miracle and there was no way she'd last another couple of decades. However Haruyuki and Utai overhear their conversation, and Utai shares a story how after her brother had died, she met a lady at the hospital who had just left an ICU after being given successful treatment with a drug for an incurable disease. Furthermore, the ICU the lady used was Medicuboid (the same type that Yuuki uses)! Hearing that people with incurable diseases were still alive in the future, gives Yuuki (and all the fans) hope that: Yuuki will live!
Leafa has a heart-to-heart with Rin after hearing her brother is in a coma. Leafa recounts her own experiences at having Kirito in a coma during the SAO incident. Leafa tells Rin that no matter what she should never give up hope on her brother and keep encouraging him to come back to her.
There's a very touching scene where Kirito and Yuuki had been sparring with Photon Swords, but after several consecutive duels, Yuuki is flat out exhausted. Kirito offers to piggyback her back home. Although hesitant at first, after hearing Kirito has done this before with Yui and Suguha, Yuuki accepts. Yuuki remarks how this must be what it felt like to have an older brother, to which Kirito tells her he'd be happy to be her older brother anytime she wanted him to.
Kirito and Asuna never got a proper wedding ceremony in canon, so they get one in the mobile game after completing a quest to help an NPC bride and groom find each other.
A slight one outside of the SAO universe: in the fighting game Dengeki Bunko Fighting Climax, both Kirito and Asuna are playable characters. The game shows that even in another universe, they still love each other and the two are even shocked at the revelation of fighting the other if you decide to pit the two of them against each other. However, the biggest heartwarming moment comes when Asuna uses her strongest attack... which is Yuuki's Mother's Rosario. Even after she's long gone, Asuna still continues to remember her friend by using the move she entrusted to her. Now THAT'S true friendship.
Fridge Brilliance then kicks in when they announced a free DLC character for Ignition... Yuuki Konno herself!
The sisters' bond in general, particularly when Aiko selflessly insists that Yuuki be able to test the Medicuboid, and with it, get a clean room and a better standard of living.
Yuuki's Character Development, particularly her epiphany around the time she, her sister and Merida plan on forming the Sleeping Knights.
She did not know how much time she had left. But if her life was to be shorter than others, she would only need to run on accordingly, at a faster rate, with a larger stride.
Merida snaps her SAO memory card in half as a birthday gift to the sisters, signifying that she's abandoned her desire to try to enter SAO and risk her life.
After Ronye gets a fever from overworking herself and not getting any rest due to constantly waiting for him to show up to give her report, Kirito gathers ingredients to make herbal remedy for her and promises to start arriving sooner.
After avoiding expulsion by beating a pair of Elite Disciples, Azurica informs Ronye and Tiese that as a condition for them staying they can't choose a new pair of mentors. The both of them have no problems with this, viewing Kirito and Eugeo as their only mentors.
When Eugeo asks Kirito what powers his sword, or more accurately what makes his Incarnation more powerful, Kirito lets slip that it's Asuna.
Alternative Title(s):Sword Art Online The Movie Ordinal Scale