Taichi's attempt to get Sora to go to his game, showing how the both of them still see each other as close friends.
After trying and failing to get any of the others to come and see his soccer game, Taichi is feeling dejected. In an last ditch attempt, he tries texting Sora (whom he never actually asked since he saw her being asked to attend Yamato's concert on the same day). After sending the message, he puts his phone away, clearly not expecting any results. To his surprise however, Sora responds immediately.
Afterwards, he hesitates to ask her to come along, settling for just telling her about the game. Again, he seems to not have much hope about the situation. However we then cut to Sora who is now desperately trying to find an outfit to wear, panicking as she tries to figure out the timing to make it to both the game and the concert.
Jou doesn't make it to the fight at Haneda Airport, so Gomamon says he'll go find him. We see Jou sitting dejected at his computer, reading the news about the monsters in mounting horror... until Gomamon knocks on his window and Jou goes to hug him, almost in tears. Cut to a silent flashback of a very uncharacteristically angry Jou telling off The Men in Black who tried to take him to Haneda. Later, when he finally makes it to a meeting with the group, he's apologetic for always having to study, but everyone forgives him because he's in his final year of school before college and Mimi runs up to give him a great big hug (and his share of the candy she brought for everyone).
Mimi giving candy to all the Digimon. It's a very sweet moment, because it occurs right as she arrives, after the fight with the Kuwagamon. What makes it sweeter is that she gives the first gummy worm to Agumon, who had been severely beaten up in the fight. What's more, during that time, the others were essentially getting depressed due to the damage that has been caused, especially Taichi. Mimi, being who she is, was able to get the entire group out of their depression with her presence.
Meiko and Meicoomon are immediately accepted as part of the team by the others, with Mimi in particular being absolutely thrilled about their new addition. Even before the two are reunited, the group offer to help Meiko search for Meicoomon and she quickly becomes friends with the girls during their outing.
Koushiro blushing in general. It's really sweet to see our favorite computer nerd acting all Adorkable about clothes and liking girls. Whenever Mimi is near, expect him to get as red as a tomato.
After hearing news of the Greymon/Kuwagamon fight at the airport, Takeru calls someone on the phone telling them that the concert will be canceled and not to come. Yamato teasingly asks if it's his girlfriend to which Takeru responds "Don't worry. I still love you the most."
There's been a social network set up for the Chosen Children worldwide, which Takeru uses to warn them of the recent attacks. The fact that the team are still in communication with their international counterparts is heartwarming in itself, and shows that they're not forgotten.
Taichi flashing back through all the images of collateral horror he's seen recently... and ending with the memory of Yamato holding his hand right before Wargreymon and Metalgarurumon evolved for the first time. He understands less, but he understands that Yamato's always been there for him, even when they're at each other's throats. That they can fight to the point of awkwardness, yet without ever doubting their friendship and trying to talk it out like adults without coming to blows says a lot about how they've grown up.
While the news were talking about the Digimon attacks and showing interviews of distressed citizens, Mrs. Yagami turned to Tailmon and Agumon in understanding to subtly call out the reports by assuring them that she doesn't find them scary and gives them a sweet, motherly smile.
Koushiro's work ethic becomes heartwarming when you realize that while the other Children have been reconnecting with their partners, overcoming emotional matters and generally reflecting and reconnecting, Koushiro's timeline of events is somewhat different. He spends the first night after Kuwagamon's attack evaluating information and clarifying the situation to the others in a presentation nobody listens to. He spends the next night creating an entire cyberworld the Digimon can exist in and access functionality with his laptop. He spends the night after that one building special goggles to allow Taichi to see disturbances, bearing in mind that Koushiro's primary skill set is programming, not engineering. On top of that, he also has to meet up with the others and attend school like everyone else. Why does he works himself to the bone like that? Because his friends need Taichi to lead them, Sora to care for them and Koushiro to handle literally everything technical.
Taichi's reunion with Agumon during the Kuwagamon attack. It's been three years In-Universe since these two last saw each other and their exchange is just very nice to watch.
Agumon: Taichi! You've grown! Taichi: And you've gotten smaller!
This scene gets even more heartwarming in the dub, since tri is Joshua Seth's first voice acting role in years, giving it really touching Reality Subtext.
In an odd way, the whole reveal about Jou having a girlfriend. The dialogue indicates that she's still dating him, despite him not being able to spend any time with her. It's sweet for someone to see Jou for the reliable person he is even when everything in the world is trying to keep him from keeping his word.
At the hot springs, Takeru checks up on Meiko to apologize for planning her welcome trip to the hot springs when she didn't seem comfortable with it. She learns that Yamato is his brother, and Takeru even gives her permission to call him by his first name.
At the hot springs, when the girls go over to the mens' side to rescue Biyomon and Meicoomon, Hikari slips on a washtub. Takeru immediately catches her and, even though she's embarrassed about seeing him naked, he doesn't mind.
Mimi and Meiko become friends really fast, and Mimi even starts calling her "Meimei." When Mimi gets called egocentric and selfish by Koushiro and her other classmates, Meiko is the only one to cheer her up and openly support her idea of running a Hooters-themed café for the school festival.
The talk between Mimi and Joe in Act 2, regarding their respective issues (Mimi being called an egocentric, self-centered girl and Joe not showing up when they needed him). Joe reassures Mimi that she's fine being who she is, at least it's better than him, which is a nice Call-Back to when Mimi asked him all the way back in Adventure if he thought she was selfish for refusing to fight (ie. doing what was right for her over what was right for the group and the world) and Joe telling her instead that she was brave. You would expect Joe to be the most frustrated with Mimi's self-centeredness, given his dutifulness and lip-service to becoming an adult and properly joining society— the same traditional society that Mimi is currently chafing under. Instead, he ends up being the most sympathetic, telling her that she's fine being who she is, even when she admits to agreeing with the criticism.
At the climax, when Joe's realization results in Vikemon, Mimi teases him about being annoying and self-centered, too. Joe laughs it off and repeats his insistence that Mimi is fine the way she is, which in turn strengthens Mimi's resolve and results in Rosemon. A bonus in the dub where Mimi's crest is not purity but sincerity; the dub made it clear that the meaning behind her crest is that she's always true to herself—and now being true to herself is what allows Lilymon to digivolve.
The focus on the close and sympathetic relationship between Joe and Gomamon in this Act::
Gomamon does not pester Joe about why he doesn't want to be with the others, and instead helps out with other chores such as preparing meals for Joe (with egg added).
When Gomamon leaves, Joe's clearly heartbroken, and rushes to the school festival the instant he receives news that Gomamon is there. And, from Gomamon's perspective, he left Joe because he knows Joe doesn't want to confront with being a Digidestined for now, and that his presence will always reminds Joe that he is a Digidestined.
Joe apparently intends to introduce Gomamon to his as of late unseen girlfriend. Not only does he do this because he "wants both of his partners to get to know each other", but Joe's lines when he talks about his girlfriend are adorable—most notably, he comments that there is a chance that she'll become his "lifelong partner" someday. Joe, who for nearly the entire first half of season 1 was ambivalent, cautious and terrified of practically everything, is so in love with this girl that he's already convinced that they'll be married someday. D'awww.
Koushiro, in searching for a way around the reboot that wiped all the memories of their Digimon partners, began to hole himself up in his office and neglect taking care of himself. Mimi's the only one who bothers to clean up his mess (even leaving behind a new bottle of his beloved Oolong tea), showing that platonic or not, she cares about him, even despite their quarrel earlier in the movie.
During the climatic battle, all of the infected Digimon snap out of it long enough to force Meicoomon into the distortion so that the human world will be safe for their partners. And before entering, they all hug HerculesKabuterimon before he walks into the distortion. This may have been to allow him to push them in while they still had control, but it could also have been as one last goodbye before losing their memories. Also doubles as a tearjerker.
When told that the gate to the digital world is unstable and they may not be able to return, each of the chosen children still decide to go if it means seeing their friends.
At the end, Nyaromon and Tokomon argue over Nyaromon's whistle. Note that because of the reboot, Gatomon never had to serve or suffer under Myotismon. Watching the most mature of the Digimon argue with the least mature over a toy really drives that point home. The reboot essentially erased her being lost by Gennai, waiting alone for Kari and feeling abandoned, and being taken advantage of and abused for years.
Yamato awkwardly reassures Taichi that they won't need to rely on Omegamon so much anymore, now that Gomamon and Palmon can reach Mega. He's still upset, but trying to be less adversarial about it.
Yamato going over to Takeru's apartment to check up on him when he feels that something is bothering him. And despite Takeru not saying anything about it, he's right.
Yamato immediately hugs a crying Takeru after the battle with Meicoomon ends.
Meicoomon is finally going be redeemed/cured. While she is still carrying the corruption, she is aware of it and struggles to not go as feral and vicious as she had done before for Meiko's sake.
Most of the Digimon quickly bond with their partners despite having lost their memories.
Gabumon is nervous about being informal with Yamato, and Taichi reassures him that Yamato would love to be called by his first name.
Agumon and Gomamon really want to talk to their respective partners after viewing some of Koushiro's pictures of them.
Nyaromon quickly befriending Hikari because she smells like her whistle. She spends the majority of the movie cuddling with her, too.
Takeru asks Tokomon if they can be friends. Tokomon looks like he's about to reject him, but suddenly yells, "OKAY!!"
After being cold for most of the movie, Piyomon saves Sora from Gennai.
Before Tentomon evolves to help fight, he leans on Koushiro's arm.
While the situation makes the feeling unable to be shown in the scene, Gennai states that the reboot will allow the Digimon who died in the human world (which means permanent death) to finally be revived. That means Wizardmon and Leomon who died in the human world will eventually return to life, even if they won't remember what happened to them.
In a Flash Back, Daigo tries to cheer up an overworked Maki and gives her a Love Confession. It's entirely bittersweet how he tries to comfort her and shows how much he cares about her.
Takeru states once again that Yamato is his number one.
Even though it takes a while for them to notice, Taichi and Yamato are the only ones to notice Sora is upset, even though neither of them know why or how to comfort her. It shows that they really care for her when they continue to check up on her during the movie, including rescuing her from Machinedramon twice and protecting her. Natsuki Hanae even said that he nearly cried when recording the scenes with Sora.
When the group gets separated, Takeru ends up in the Primary Village. Based on how the other Digimon reacted earlier in the movie, you'd think Elecmon would attack him, but the next time we see him, Takeru is happily babysitting the Digimon while Elecmon treats his wounds. Even though Elecmon doesn't remember him, he's still very friendly and wants to meet Patamon after hearing Takeru talk about him.
In Adventure, when Yamato was convinced he was better off alone:
Gabumon: I've waited in this world forever just so I could meet you, and only you!
In Tri, when Gabumon asks why Yamato risked his life to save him:
Yamato: I didn't want to lose you again. I came to this world to see you, no one but you!
Cue Digivolution into Metalgarurumon.
As Kari is staring at the final villain she, unwillingly, has a hand in unleashing, who is the first to go over to try and help her? TK.
Agumon's conversation with Meiko, telling her that even though she feels guilty about Meikoomon going berserk and causing trouble for everyone, that it's not her fault that it happened, and what happened to Meikoomon isn't her fault either, which results in Meiko tearfully hugging him.
Yamato tries to comfort Sora about Taichi being gone, which is nice when you consider that he had trouble realizing why she was upset in Loss.
Yamato is stressed out upon becoming the new leader, but Gabumon comforts him, vowing that he will always stay by his side no matter what. Gabumon even promises to take care of Yamato when he gets old, and also says, "I'll even save the world for you."
During the Final Battle, the Digimon regain their memories of their human partners.
After the Final Battle and losing Meicoomon, Meiko has to move back to Tottori. Around Christmas time though, the Chosen send her gifts and get Taichi to call her and wish her a Merry Christmas from the lot of them. Not only does it reaffirm that Meiko will always be one of their True Companions, but with the way the others are trying to get Taichi to talk to her as he blushes, they look like they're trying to get Taichi to stop beating around the bush with Meiko.
The ending theme, hands-down. It's Butter-fly, performed by the entire cast. It starts out with Kouji Wada's vocals, without any background music, as if his spirit is singing beyond the grave, before the music kicks in and the rest of the cast begins singing. Near the end of the song, his vocals join in again one last time to close out the song. It's essentially one big heartwarming tribute and send-off to someone who was so involved with the series for years. As an added bonus, it's not just Kouji Wada and the voice cast who get singing parts - Ayumu Miyazaki and AIM both get a hand in the song as well, showing that they, too, have been important to Digimon Adventure!
Jeff Nimoy's responsibility for bringing Joshua Seth back into playing Tai. Nimoy had made a cheeky post on his Facebook page about voicing Tentomon. Seth legitimately had no idea that dubbing was even being considered for tri., never mind already in progress, but Nimoy was more than happy to give his friend the proper contact information. Just like that, Seth was welcomed back into his signature role. note Remarkably, this was the second time Nimoy gave Seth major assistance on voice acting in Digimon, as he took over Tentomon's voice from Seth early in Adventure.
Lara Jill Miller wrote on Facebook and tweeted a message thanking fans for their support a few weeks after the announcement that she was not reprising Kari. Somewhat bittersweet, it provided some closure to long time fans who were not happy with the change.