Sekai is pretty adept at making his gunpla make use of Plavsky particles for his special attacks, despite having no prior knowledge of anything gunpla related beforehand. How is he doing this? He is a martial artist, so despite not knowing plavski particles being able to enhance gunpla attacks, he is very familiar with the concept of chi/ki, and its relation to martial arts. He's applying the knowledge of chi manipulation in gunpla battling, similar to Nils and his particle Fa Jin, which does the same thing.
Not only is the Build Burning hidden inside a Dom, it's also hidden inside Sei and Reiji's trophy. That seems like a pretty ridiculous place to hide it, until you remember that the person most likely to handle the trophy aside from Sei... is Reiji, for whom the Build Burning was most likely built for.
Confirmed in Episode 18, the Build Burning was built and tuned with Reiji in mind.
The Build Burning Gundam sure is powerful, ain't it? Well, it was built by Sei for one... but take a look at it. Parts of it are glowing blue while it's active, with the same sparkle effect that the RG System in the first season had — The Build Burning Gundam is in perma-RG. Basically, the Star Build Strike's Super Mode is the Build Burning's standard mode.
Shimon Izuna only fights with a snap-built model, which is implied to have been built by his ill brother Mamoru. The most probable reason why it isn't a modified model is because customizing a gunpla is a painstaking and tiring work, something that Shimon's brother doesn't have the stamina for. Also, Mamoru builds with only the barest of tools and parts at his disposal, with his brother mainly prioritizing more important stuff, such as food and medicine, so whatever that's left is usually spent on Mamoru's hobby of getting new models instead of customizing one.
All things considered, Gunpla is a fairly cheap hobby if you just snapfit, with your only tools being a pair of nippers. Getting all the things for customisation - paints, Gundam markers, brushes, advanced tools - is what really drives the cost up.
In a quick shot, they show a pair of nail clippers in Mamoru's room. He probably uses those in lieu of nippers, meaning the only cost is the models themselves.
Also, if Mamoru's ailment was to do with his respiratory system, the fumes from cement, paint thinner and other similar substances would probably aggravate it, so he might not have been allowed to use those. The only tools seen in his room are the nail clippers and a pair of scissors. Although the close-up shot of the Destiny model in that episode made it look like he might have been using the cement technique for seam-filling...
As it was in Build Fighters, most characters use customized gunpla models, which are stated to perform better than snap-built (unmodified models that are built simply as the manual states) kits in gunpla battle. Why is this so? This is because people who customize a gunpla model use other materials (like metal parts for the boosters or actual cloth for capes) in the hopes of making their models more unique. They also use adhesives to make their models look more like one piece instead of several pieces, paint and coating to prevent wear and tear, and some go as far as to build parts from scratch. All of these customization tends to have an effect when the gunpla is animated with plavski particles. For example, a metallic paint with a glossy coat would likely have an effect similar to laminated or beam coating, or going back to the Build Fighters matches, the Kampfer Amazing had grease to prevent bombs from sticking on its joints, and Sei put a lot of super glue on the Star Build Strike's arms to prevent Plavski particles from destroying it from the inside during his match with Nils. To make a long story short, any form of customization on a gunpla model will give it additional benefits in gunpla battles, hence why most people say customized kits are better than straight-build ones.
Yuuma's suicide trap against Sudou in Episode 9 seems to be an attempt by the former at Taking You with Me. Then you realize that he had his Lighting's Back Weapon System separated the entire time meaning that he planned to survive the attack. The only reason everyone thought he was out was due to the fact that he had lost contact with his teammates.
Sekai somehow being able to feel Build Burning Gundam's pain seems a bit out there. Then you remember the Plavsky particles could mentally connect two people and transport them between dimensions. It doesn't seem so farfetched anymore.
Yuuma being able to upgrade the Build Burning into the Build Burning Try makes even more sense, when you consider that he's likely been repairing that Gunpla since the start. Considering how many times Sekai damaged Build Burning, especially after that fight with Shimon, Yuuma's likely been carefully repairing it behind the scenes in addition to his own unit. He knew and learned from Sei Iori, so he'd better equipped than anyone else to work on the Build Burning.
It seems odd that Sekai is well aware of Yuuma's crush on Mirai yet is oblivious to Fumina and Gyanko's crushes on him. But when you realize that since everyone basically swoons over Mirai everywhere she goes he's probably both 1) seen it enough to recognize when someone's crushing on her and 2) Associates crushing on someone with the instant theatrical swooning everyone does for Mirai which of course didn't happen with him. Not only are they significantly more subdued but they also took awhile to warm up to him.
Wilfred asking Shia to fight Kei Karima's team alone seems out of character for him, but it's likely that he wanted to punish Karima for making light of Sekai and not fighting seriously while they were training at Nielsen Labs. By sending Shia alone, he denied Karima a chance to fight Team Celestial Sphere and made his defeat even more crushing.
7 years later, we have the Damage Level system. But why? Remember at the final battle in the last episode of the first season, Reiji gave Sei a speech about how what was holding Sei back was his fear of damaging gunpla. Nils was there to hear it, and now he's involved with the development of the battle system. Nils probably realized that 1:1 damage was scaring a lot of people away from Gunpla Battle, who otherwise would love it. Implementing the damage levels allows for people to gradually ease into the game, and not have to worry about repairs to their gunpla. They would eventually build enough skill and confidence to play at tournaments where the damage levels are set higher.
At the same time, the damage levels allow the system to cater to all levels of play and commitment (and for what it's worth, Damage Level B is consistent with the damage levels we see in Season 1).
Why is Sekai able to instantly activate the Build Burning Gundam's Super Mode when it's revealed inside of the Dom but unable to do it in subsequent battles? Because while he was piloting the Dom itself, the particle use was probably very low, allowing the Build Burning Gundam inside to gather particles until it is released and make it easy for him to use it. In later battles, because of his fighting style's use of particle emissions to do pretty much anything, it becomes impossible for him to utilize it until he gets the hang of assimilation.
Everyone views the Tryon 3 as being impractical, but for all of its flashiness, there's a pretty big advantage of having 3 machines combine into one. The rules state that you can either have three Mobile Suits or one Mobile Armor. Earlier in the series we see Mobile Armors that use combining/separation tactics with each part piloted by a different member. The game counts the Tryon 3 as a Mobile Armor, not a Mobile Suit, because it is 3 separate units combined; and this allows it to have the power of a Mobile Armor, just in a smaller size.
There's a lot of fridge brilliance in the Try Fighters' mecha if you think about it.
All of them have four-pointed V-fins just like the Build Strike Gundam, a nod back to the pioneering Build Fighter.
Yuuma's the one who idolises Sei Iori the most, yet can never bring himself to surpass that level on purpose, which is why the Lightning Gundam mimics the Build Gundam Mk II color scheme instead of the Build Strike. Worth noting is that its modular rifle mimics the Build Strike more.
All three mechs share the same colors in varying degrees with notable excaptions - Lightning has a deep blue instead of vivid blue, indicating his usual aloofness; and Winning has orange instead of red. Not like Sekai's mech at all. Not for any specific reason and I don't know what you're talking about.
And of course, Star Winning can mimic the Plavsky Power Gate, Lightning can mimic the blasting finisher and Build Burning can mimic the Build Knuckle.
Lightning Gundam's overall design carries an additional level of brilliance - Build Strike as we all know is based on the Strike Gundam from Gundam Seed, where the first season featured the Strike, the generic backpack-enhanced mech, and Seed Destiny has the Impulse Gundam, also backpack-enhanced and divides into three parts for transportation. Both end up referencing Mobile Suit Gundam and Mobile Suit Gundam ZZ, leaving a glaring gap where Mobile Suit Zeta Gundam should be. Cue the Lightning Gundam - has a flight mode just like the Zeta, and uses several backpacks just like the Seed line, essentially acting as the missing link.
More on mecha design — Build Burning Gundam has a spherical piece forming its midsection, which not only makes for exceptional waist articulation that a martial arts unit would need, but goes a long way into explaining how Gundams like this one and all the ones in Mobile Fighter G Gundam can be Mo Cap Mecha — the pilot's in a mini-Cerebro sort of spherical room that allows ultimate freedom of movement.
Something between Fridge Heartwarming and Fridge Tearjerker depending on where you stand — the original Beargguy F main unit aka Mamagguy is depicted as performing a Heroic Sacrifice for its Petitguy, and in the last episode, Mirai is still using a Petitguy, giving the impression that Mamagguy had been Killed Off for Real. Then Island Wars takes it up to eleven with the new Beargguy P, which is essentially Beargguy with angel wings and a halo — which means that Mamagguy Ascended to a Higher Plane of Existence.
Meijin joins in on the battle royale and says it's his second childhood makes more sense if you remember that in the last series, he was forced to leave school early to take on the title of Meijin. And because of the events of that series, he fought what he thought would be the final gunpla battle ever with a machine that was pieced together with scraps (and he didn't even get to finish that battle either). Here he gets to relive that battle, but with his machine and nothing on the line.
Fridge Horror
The idea of assimilation, i.e. the Gunpla Fighter feeling what the suit suffers. This may be downplayed in a lighthearted series like GBFT, but the idea has already been explored horrifically in Mobile Fighter G Gundam and Neon Genesis Evangelion; and let's be honest, Sekai's usual collapses after battles where he "assimilates" just look like injured fighters in boxing and/or Mixed Martial Arts.
A case of Fridge Tearjerker if there ever were one. In episode 18, it's mentioned that Sei "sealed" the Build Burning Gundam alongside his memories. When you consider that the Build Burning was built for Reiji (looking at the color scheme of the Build Burning, it's pretty much harkening Reiji's own color scheme/fashion), then it's likely that he sealed it because he never got to see Reiji again in the seven years between the series.
This is in addition to the second OP, where you see a dejected Sei's shadow turning and walking away, with the championship trophy that contains the Dom that hides the Build Burning, sealed up in a cupboard, signifying Sei has given up waiting for his friend's return.
Also more of a Fridge Tearjerker, but The Stinger of the Island Wars OVA reveals that the little girl's parents were none other than Aila and Reiji. If you watched the original, you would know that Aila grew up as an orphaned child. This means the little girl will never have a chance to meet her grandparents or any other relatives from her mother's side back in Finland.
