Osamu and the others continue to train at Tamakoma Branch, with Kyōsuke trying to find different ways to help Osamu train. Later, Mr. Kido sends Border's top three teams along with Miwa Unit to retrieve Yūma's Trigger. As they move towards Tamakoma Branch, they meet Jin, who reveals he foresaw their attack, and he and Arashiyama Unit join forces to battle the Raid Team in order to protect Yūma from them.
At Border HQ, a gate opens, and the ship with Border's Top Teams returns from their away mission. Over at Tamakoma Branch, Yūma is observed stretching outside with Raijinmaru (in perfect sync, no less) by Kodera and Yoneya of Miwa Unit. Osamu and Chika arrive, and Kizaki offers the three breakfast (triple meat and some vegetables). Kodera makes minute observations and takes detailed notes of everything occurring inside Tamakoma Branch, but Yoneya says he has no hard feelings towards them and takes little interest in their reconnaissance on the Black Trigger.
At HQ, Kido is presented with four unknown triggers by Isami Tōma, Sōya Kazama, and Kei Tachikawa. Kido immediately orders them to retrieve the Black Trigger at Tamakoma Branch. Narasaka relates the details of Miwa Unit's encounter with Yūma, Jin's intervention, and Yūma's subsequent acceptance into Tamakoma Branch. Kazama is not surprised by this information, recalling that Tamakoma's previous engineer was a Neighbor. Kido orders them to use any means necessary to obtain the Black Trigger. Narasaka fills the group in on Yūma's daily schedule, and Tachikawa surprises everyone by saying they will attack tonight. Miwa cautions them to not underestimate Yūma, but his warning is brushed off, leaving Miwa to reflect on how he has never liked Tachikawa.
Back at Tamakoma, Kizaki instructs Yūma on the correct way to eat his first sandwich and Chika's Trion level test reveals that she is at super A-Rank, or Black Trigger level. Both Chika and Yūma are praised by Kizaki and Konami, but Karasuma only says they should have hope for Osamu's future. When Konami says they don't need weaklings at Tamakoma, Karasuma lies and says that Osamu called her cute, causing her to blush happily. Karasuma quickly retracts and says it was a lie, and Konami pounds on Osamu in retaliation. As they return to training, Osamu resolves to become stronger to match his teammates. His training; however, consists of doing housework. Karasuma explains that the technique of turning cleaning movements into fighting strength came from an old movie he watched the day before. Unfortunately, he utterly fails during fighting practice. Yōtarō then joins Osamu's training, implementing a karuta game, which Osamu loses to both Yōtarō and Raijinmaru.
Elsewhere in the Forbidden Zone, the teams are speeding toward Tamakoma Branch. Again, Miwa thinks he has never liked Tachikawa. They pull up suddenly when Jin appears in front of them and casually asks where they are headed.
At the end of training, Yūma once again looks frazzled, but won three rounds against Konami. Yūma asks Karasuma for a match, calling him senpai. Outside, Kizaki and Yōtarō take Osamu and Chika for a run, in order to improve his ability to use his Trion body.
Jin and Isami exchange friendly pleasantries, but are cut off by Kazama. Jin asks the group to leave Tamakoma's new recruits alone. Isami seems hesitant to fight Jin, but Kazama reminds Jin that it is against Border's rules for agents to fight one another. Jin turns this back at him, stating that Yūma is also a Border agent now, so their mission is also against the rules. This infuritates Miwa, and Tachikawa counters by saying that Yūma cannot be considered an fully-authorized Border agent until the recruitment date in a couple of weeks. Until then, he is simply a Neighbor. At this point, Miwa realizes that the reason he doesn't like Tachikawa is because of his similarity to Jin. Kazama tells Jin that Kido will do anything to obtain Yūma's Black Trigger, and they will eventually succeed. Jin replies that it isn't just a Black Trigger, but more important to Yūma than life itself. Jin also admits that at best, even his Black Trigger would be an even match against the strength of Border's top teams. However, he isn't alone. Just then, Arashiyama Unit shows up, under orders from Shinoda to assist Tamakoma Branch. Arashiyama says he owes Osamu (see Episode 3), and Jin says that with Arashiyama Unit on his side, even his Side Effect says they will win. Tachikawa draws his Trigger, and decides he wants to prove Jin's Side Effect wrong.