For most of the Third Group to be orphans and such, they have really strong ties to one another.
Mika and Orga in particular, due to their (currently) unclear shared past. Orga admits to Biscuit in private that the reason he leads Tekkadan into increasingly dangerous situations is because he must be the coolest Orga in Mika's always expectant eyes, and he can't let him down.
Biscuit being a good brother to Cookie and Cracker. He joined up with CGS to look after them, exposing himself to all sorts of bloodshed and potential abuse. And they clearly care about him enough to hitch-hike all the way to where he's stationed.
Mikazuki choosing to eat the food Kudelia prepared in the third episode, despite her feeling it was inadequate for anyone else to. She was clearly sensitive about it, and was grateful about it.
Mikazuki treasuring the bracelet given to him indirectly by Atra, even going so far as to shield it from being in sight of a Mercy Kill.
In the fourth episode, Mika sincerely thanks Kudelia for all of her help since it has given them all a place to keep going to.
Kudelia offers to teach Mikazuki how to read and write so he can perform maintenance on his mobile suit better than before. The Tekkadan kid workers overheard Kudelia providing education and also wants to be in her curriculum. The excitement to learn how to read and write are further demonstrated by the children addressing Kudelia as "Kudelia sensei".
When Naze Turbine offers Tekkadan to put them in non-combat roles if they surrender to Teiwaz, he off-handly mentions that since there's a lot of people, they would probably be split into several groups. As soon as he mentions that, Orga looks at Mika, who quips: "I don't want us to be separated", which Orga immediately takes as reason enough to tell Turbine to stuff it. It goes to show how much the CGS kids are a tightly-knit group, and how much they value each other
Naze Turbine is visibly disgusted when Maruba told him that if any CGS kids have no Ālaya-Vijñāna system, then they were of no use to him. This coming out of Jupiter's mafia...
Seeing Kudelia and Atra spending time with Amida, Lafter, and Naze's babies is just so adorable it (almost) makes one forget about all the horrible things that have transpired.
Everything about Orga accepting the view of Tekkadan as his family; and how he'd do anything and everything to make a good home for them to be proud to return to.
Biscuit and Takaki share a bonding moment with the common goal of earning enough money to send their little sisters to school.
When Takaki is hurt and Akihiro blames himself, the rest of Tekkadan shares the blame with him and tells Akihiro that he's worth more than he believes.
A minor moment on Episode 12, but when Kudelia's concerned about Mikazuki being on a dangerous scouting mission, Atra held onto Kudelia's hands and reassure her to have faith in Mikazuki.
Tekkadan holds a funeral for all those who died in the battle, including Akihiro's brother, Masahiro.
how Orga deals with the surviving Brewers Child Soldiers: he offers them a place in Tekkadan and treats them as human beings instead of human debris.
Wife Husbandry vibes aside, McGillis actually takes his engagement to Gaelio's kid sister in stride. Despite being mocked over the Jail Bait Wait, he's incredibly respect towards her, only wanting her to be happy.
Episode 15 prominently features Atra and Kudelia's sisterly relationship. After she and Biscuit are captured, Atra pretends to be Kudelia; brushing off a brutal beating at the hands of Gjallarhorn soldiers, all out of concern for her. Kudelia meanwhile expresses tremendous distress after hearing about their capture, feeling very uncomfortable being told to lay low and hide while Mikazuki rescues them.
There's also the clear concern that Mikazuki displays for Atra, briefly displaying a desire to murder her and Biscuit's captors after seeing her state from aforementioned beating. He's talked down easily enough, and settles for carrying her off over his shoulder.
Episode 17: Though Orga issues orders to Tekkadan to fight off Gjallarhorn, the Turbines must abstain; it's clear though, that they want to help fight (Lafter and Naze in particular), but are bound by their connection to Teiwaz to stay neutral.
In the Gjallahorn side, Gaelio shows respect for Ein despite his subordinate's status as a half-Martian. As a matter of fact, Gaelio's words of encouragement reminds Ein back when Lieutenant Crank first met Ein.
In episode 19, Mika finally shakes Kudelia's hand.
In episode 23, after the deaths of their comrades, especially Biscuit, the children in Tekkadan will now always remember their fallen comrades and avenge them at all cost, like a real family. They will now stand on the field and watch Mika wiping out every last one of their enemies.
This episode shows that Takaki still keeps Biscuit's hat with him, who then wears it for Tekkadan's Final Battle with Gjallarhorn.
Kudelia is wearing the Tekkedan jacket. More than that, she's wearing it when she's telling off Macani for his lack of faith in Tekkedan. It's quite a show of solidarity.
Episode 25 shows that Mika finally returns Atra's feelings.
The opening of Season 2's first episode shows Mika and Orga standing at the top of a cliff overlooking Sakura's fields, where they've built a monument dedicated to all of their fallen comrades, with all of their names engraved on it.
Also in the first episode, Mikazuki and Atra are picking up Cookie and Cracker from school, which is adorable enough in it's own right. However, it becomes even more so when you realize that Biscuit's lifelong dream of sending his sisters to school is now a reality! Even if he wasn't there to see it for himself.
Kudelia has her new company which she has named Admoss.
Tekkadan refuse to use the Alaya-Vijnana system on new recruits.
In episode 2 Atra gives Kudelia a bracelet that forms a matching set with the ones she and Mikazuki wear, so that the three of them can be together no matter where they are. Kudelia is briefly left speechless, overwhelmed with emotion.
Episode 8 has Takaki deciding to leave Tekkadan behind. Everyone supports the decision to cling to the happiness he has now, rather than risk losing him in battle.
Episode 10 reveals Kudelia has named a school after Fumitan and gives free tuition and lunch so that children won't have to become soldiers to eat. It's her way to improve the world.
Episode 12 gives us a hilarious moment between Yamagi, and Shino, when they're enroute to the canyon to fight Hashmal. The latter having the former sit on his lap, whilst rocketing across the landscape.
During the Turbine's farewell to Tekkadan, Lafter is grilling Akihiro for getting himself knocked out during the fight with the Mobile Armor and fighting recklessly in general. Akihiro agrees and admits that he will fight smarter for now on since Lafter and Mikazuki were the only two pilots he really trust to having his back.
Naze calls McMurdo and begs that he take in the rest of the Turbines. When McMurdo allows it, Naze gives a small smile.
Amida reveals that Naze planned on giving only himself up so the rest of the Turbines can escape, while also protecting Tekkadan. Of course Amida isn't going to let that happen.
As Orga is desperate to save Naze, Akihiro and Shino arrive to tell him they want to save the Turbines too. They reveal a plan in which they plan to save the refugees with Ride. Orga even bows his head to them, begging that they rescue Naze.
When Lafter runs out of ammo, Akihiro arrives just in time to save her. As she asks why he's there, he replies that he doesn't need a reason.
After Ride takes down one of the Gjallahorn units, Azee praises him on becoming a better pilot. He gives the compliment back by saying she was a great teacher.
Mixing with Tear Jerker, as Naze is dying we see Amida's spirit embrace him one last time.
Mika comfortingly holding Atra (with his one working arm) as she cries into his chest over Naze and Amida's deaths. Possibly the one warm moment throughout the entire montage.
McMurdo decides to hold Naze's funeral in Teiwaz's headquarters despite the fact that Naze officially wasn't part of Teiwaz at the time of his death and holding his funeral would look bad.
Mika gets to be around the Turbines' babies for a little while, and one actually takes a shine to him. Just the fact that they don't see anything off-putting about his condition at all - they have to crawl around too!
Akihiro and Lafter's date. The two more or less confess what they mean to each other, and while it doesn't end with them becoming a couple, it was definitely interesting see Akihiro in particular being so open with his emotions. Which makes Lafter's death later in the episode more tragic.
As McMurdo looks at Orga's broken cup, he states that due to their hot-headness Tekkadan is useless as an organization. But he admits he's touched by how loyal they are to Naze.
Merribit revealing that she quit Teiwaz and is sticking with Tekkadan as she wants to help the children and she cares about Yukinojo.
Episode 18: When Lord Bauduin sees Gaelio's speech, he collapses in relief in the knowledge that his son is alive. A rare moment of joy in an otherwise quite disturbing episode.
Mc Gillis going out of his way to stop Almiria from killing herself despite the fact that now that he has acquired Bael, he doesn't actually NEED her anymore.
When Atra starts to cry at the thought of Mikazuki going into the deadliest battle of his life and makes an Anguished Declaration of Love, Mikazuki hugs her, thanking her for teaching him how precious life is beyond the battles which he grew up with.
After the retreat, Derma lost his left arm and contemplates that he feels useless and wishes that he should have died because he's a Human Debris. Fortunately, Akihiro comforted him by telling him that he's grateful that he's alive despite losing an arm. Considering that Akihiro lost Masahiro, Aston and Lafter, he's really glad that his remaining adopted brother is alive.
Eugene tells a distressed Yamagi about Shino's final conversation to him: It turns out that Shino does know about Yamagi's feelings to him. It's just that he doesn't know how respond it because he considers him and everyone in Tekkadan as his family. Regardless, he vows to protect them no matter what.
Atra giving Kudelia The Glomp when she arrives. It's clear they've come to love each other.
Orga telling everyone that they're free to go if they want to, and almost everybody choosing to stay.
As Zack's packing, as he's taken Orga's offer to leave Tekkadan, he tells Dane to go with him so that the latter has somewhere to go. As for Dane himself, we get a bit of his darker backstory, and his devotion to Tekkadan comes from the fact that they still took him in even after his criminal past. As a result, Zack finds himself torn.
Nadi and Merrebit's reunion, where he tells her she should leave but she says she's not going anywhere. It's especially cute when she makes him blush.
Kudelia vows to take care of Mikazuki, Atra, and their child because she considers them all people she loves. She sticks by them when just about everyone else has left them behind, and even comes up with an idea to save them.
Also the fact that Atra is completely comfortable with the idea of Kudelia also having a child with Mika. In general, the fact the three of them genuinely love each other.
Really, just the fact that some time offscreen Mika and Atra tried for a baby, in this near-hopeless shitstorm.
Despite having Tekkadan cut ties with Teiwaz, which is irrevocable, the fact that McMurdo acquiesces to Orga's request of connecting him to Rustal Elion is a minor example. It helps that this was a favor that did not involve any kind of financial or combat aid.
Episode 23: Things finally start to turn around for Tekkadan: Orga manages to make it to Chryse, where he convinces Makanai to help fake Tekkadan's deaths. Then, we learn that Azee convinced McMurdo to let the surviving Turbines smuggle Tekkadan to Earth to repay them for everything they did to help avenge Naze, Amida, and Lafter.
Episode 24: Once Tekkadan gets news of Orga's assassination, morale is at an all time low. Half the members want to abandon the retreat and ride off in a Roaring Rampage of Revenge to avenge their fallen leader. It ends up being Mikazuki who steps up to ensure that no one rushes to their deaths and convinces them to continue to follow Orga's last order.
Akihiro: Let's live til we die, and carry out our orders.
Mikazuki: You're right. We can't stop yet. Hey Barbatos, you don't want to stop yet? Let's do it then!
During the final battle, when Julieta asks Mikazuki why he's fighting so hard in such a meaningless battle, Mikazuki admits that she is right: he has never had a cause or a purpose. However, he then remembers that Orga gave him a purpose and thinks of all the members of Tekkadan who have safely escaped Gjallarhorn's massacre. He then realizes that Orga did fulfill his promise to Mika: Mika found the place where he belongs, with Tekkadan. And then the dying Mika sees Orga agreeing with him.
It's revealed that due to the losses of Issue, Kujan and Fareed families, Gjallarhorn scrapped the Seven Stars Councils system and created a more democratic system which lead to various reforms such as Mars gaining their own government with Kudelia being their first leader allowing for even more change. In the end while Tekkadan and McGillis failed, they created a better world where no more children like them would be born.
Despite his earlier vow to Orga about crushing Tekkadan down to the last man, Rustal doesn't follow through on that once Mikazuki falls. In fact, it's implied that he's fully aware that the majority of Tekkadan's survivors, which he never pursued at all, work under Kudelia. He continues to look in the other direction.
It's shown that most of the surviving members of Tekkadan are living stable lives. Emphasis on the word "most", as explained in the Tear Jerker page.
After going through hell and back, Gaelio Bauduin finally gets to live a peaceful life. He may even getting together with Julieta, though Julieta remains Julieta.
And of course, Mikazuki manages to live on through his son, Akatsuki. Who is raised by both Kudelia and Atra, thinking of both as his two moms. And he is wearing each of their Bracelets his Mom made for the three of them.
The context of the end of Freesia's visuals, the room with the pictures of Tekkadan right after the Hashmal battle and Biscuit with his family overlooking the farm, is finally given: it is set in the timeframe of this epilogue. The last shot of the series is a zoom in on the group photo, showing Mikazuki, Orga, Atra, and Kudelia having fun.