Having met Sei by chance, the mysterious boy Reiji insists on staying at his home and somehow even ends up coming to his school. And when Gonda, a student council executive, tries to kick out this intruder, Reiji turns the tables on him as well. Tatsuya Yuki, the student council president and head of the model-building club, attempts to resolve the situation by saying that he invited Reiji to join the club. But Gonda, having lost face in front of the other students, challenges Reiji to a Gunpla battle purely for revenge. Using Sei's Build Strike Gundam, Reiji wins a total victory in his battle with Gonda. Then a crimson Gunpla appears before them both—the Zaku Amazing!
In the morning, Sei gets up for school. Over breakfast, he explains to his mother that Reiji kicked him out when he tried to get the latter up. Sei thinks Reiji is strange and has no common sense, but Rinko thinks he's not bad since Reiji was in love with her vegetable stir-fry. When Sei leaves, he tells his mom to deal with Reiji since she was the one who let him in.
On the way to school, Sei thinks back to when he proposed to Reiji to fight alongside him in the World Championship. Despite his impressive performance against Susumu, Reiji declines his offer as he only fought to keep his promise to Reiji, which was at that time over. Sei then asks about the meal, but Reiji says that it was to his mom. Back home, Reiji greets Rinko, who informs the former that Sei went to school. Reiji, to a incredulous Rinko, asks what school is. In class, Sei draws in his notebook, obsessing over completing the Build Strike before the tournament, given how he can't rely on Reiji. When the teacher calls on Sei to answer a question, he instead answers by explaining about the new beam rifle, which gets a laugh out of China. At Iori Hobby Shop, Reiji is bored about the fact there are no customers in the store.
Sei continues to draw the new backpack for the Build Strike when all the girls scream over the arrival of President Tatsuya Yuki, a ninth grader who is also Captain of the model-building club. In the club room, Sei gushes over the completeness of the club's models, though Tatsuya admits he build a HGUC MS-05B Zaku I by himself with alot of weathering, though he admits being a fan of Sei's work and having visited the family store. Sei wonders if Tatsuya invited him to join the modeling club, but the latter instead asks about the rumors of him defeating Susumu and assumes he's entering the championship. However, Sei doesn't think he can compete against Tatsuya, who was the 3rd Block Champion and made it to the World Tournament. Outside, China's friends gossip about Tatsuya when Reiji shows up and tries some of China's food. Reiji is then confronted by Student Council member Monta Gonda who tries to boot Reiji off campus. In the room, Sei explains the situation about Reiji's disinterest in Gunpla Battle when China bursts in, informing them of the fight between Reiji and Monta, which Reiji handily wins.
Monta complains to Tatsuya about letting Reiji in, and reveals that he "invited" Reiji to the school as a outstanding Gunpla fighter. Monta offers to Tatsuya a Gunpla Battle against him. Though Sei illegally brought his Build Strike to campus, the fight commences with Gonda piloting a MRC-F20 SUMO. Mr. Ral then shows up and explains to China that the Plavsky Particles were found a decade prior and only react with plastic, allowing life to be breathed into ordinarily inanimate Gunpla. Immediately, Reiji dominates Monta's SUMO, and Tatsuya gets excited over his piloting skills. Just then, the air starts being sucked out of the colony, forcing Reiji on the defensive while he charges the IF Generator. Sei tells Reiji to charge straight as the generator has a time lag. Reiji charges and wins the match. Then, Tatsuya challenges Reiji to a match in his MS-06R-AB Zaku Amazing, which made the 6th World Championship. Mr. Ral explains that Tatsuya's immense piloting skills had given him the nickname of "The Crimson Comet". Reiji charges into the fight, but the Zaku Amazing manages to dodge Reiji's attacks with its high mobility, and manages to disarm the Build Strike. Sei and Reiji are stunned they were only defeated in seconds.
On the way home, Reiji is frustrated after losing to Tatsuya after he barged into their fight. Sei frets over their lack of ability, but Reiji reminds him that Tatsuya told Sei to complete the Build Strike before the tournament and wanted to fight against it. Reiji tells Sei to finish the Build Strike to pay back Tatsuya for their loss and is determined to join Sei in the tournament. At the same time, Tatsuya notes a crack on one of his Heat Natas, and Sei promises to finish the Build Strike and make it the best Gunpla possible. Just then, Reiji glows in light and quickly vanishes into thin air, to Sei's shock.
Featured Mobile Weapons
- During the battle between the Build Strike Gundam and the Zaku Amazing, Tatsuya yells, "Moe agare!" ("Rage on!"), a reference to the lyrics of the Mobile Suit Gundam theme song "Tobe! Gundam" ("Fly! Gundam").
- When Tatsuya defeats Sei and Reiji, he points his Heat Nata at the Build Strike Gundam's head and tells them the Gundam is incomplete. This is a nod to episode 7 of Mobile Suit Gundam 00 Season 2, where Mr. Bushido in his Ahead Sakigake pointed his GN Beam Saber at Setsuna F. Seiei's crippled 00 Gundam and told him there is no value in defeating an incomplete mobile suit.
- The next episode preview tagline ("I'm seeing the tears of time") echoes the episode preview tagline of Mobile Suit Zeta Gundam ("You will see the tears of time").
- Sei requesting Reiji to stay with him because he owed him a meal is a possible reference to Double Zeta where Judau was requested to stay with the Argama for owing a debt for the food provided.
|Gundam Build Fighters Episodes|
Sei and Reiji | The Crimson Comet | Full Package | Gunpla Idol Kirara ⭐️ | The Strongest Builder | A Reason to Battle | World-level Ability | Encounters of Fighters | Wings of Imagination | The World Tournament Begins | Battle Royal | Discharge | Battle Weapon | Codename: C | Fighter's Radiance | Dad, We Meet Again | Model of the Heart | Bloodhounds | Astray's Blade | Aila's Betrayal | Amid the Glittering Particles | Meijin vs. Meijin | Gunpla Eve | Dark Matter | Promise