Neighbor and Trion Soldier

Short Summary
''After Yūma's battle with the Neighbor, Miwa Unit investigates the site and is surprised to know the Neighbor wasn't defeated by one of Border's agents. Osamu, surprised by Yūma's revelation that he's a Neighbor, questions him about it. He realizes Yūma isn't used to Earth's customs and decides to teach him about them. The next day, the Third Mikado City Junior High School is attacked by a Mole Mod, and Osamu decides to battle it to protect his schoolmates, despite Yūma's warning that he'd die.''

Long Summary
After Yūma's battle with the Neighbor, Miwa Unit comes to the local. Tōru Narasaka meets with the 3 Idiots, asking what they're doing in the Danger Zone, which is out of limits for civilians. They ask for help, explaining that they've run away from a Neighbor, and Narasaka reports to their operator Ren Tsukimi that he found civilians in the Danger Zone and one of them is hurt, and they require protection. Meanwhile, Shūji Miwa and Yōsuke Yoneya investigate the Neighbor's corpse. Miwa asks Ren who defeated it, and she asks him to wait while she investigates it. Yoneya says it must've been an A-Rank agent, to which Miwa agrees, but Ren says they're the first Border Unit to get there, leading Shūji to wonder who did it. Not too far from there, Osamu follows Yūma, telling him to wait. He asks Yūma what he means when he says he's a Neighbor, as "that thing" was a Neighbor. Yūma corrects him, saying that thing was a Trion Soldier, weapons created by Neighbors, humans like him who live on the world on the other side. He says he wasn't the one who called that thing, and proceeds to say there are different people on the other side too.

Later that day, Yūma questions Osamu for not knowing about that, despite being part of Border, and Osamu says he never heard of that, and that it sounds crazy. Yūma notes that it's different from what his father said, and Replica tells him it was a wise decision to leave the Danger Zone immediately. Yūma decides to tell Osamu to forgot what he said, and that he's 100% percent Japanese and not at all a Neighbor, and Osamu says that makes him sound even more suspicious. Yūma is bothered by this, as saying he's a Neighbor is crazy and saying he's Japanese is suspicious. Osamu asks which one is the truth, and Yūma says he's a Neighbor, but then says he's Japanese, making Osamu even more suspicious of him. He asks himself what Yūma is, noting he helped Osamu, so he doesn't believe Yūma to be evil, but has a Trigger despite not being a Border agent. Osamu decides that, as a Border agent, he has to look out for Yūma.

Osamu tells Yūma they should talk more, but Yūma says he's hungry, so he asks Osamu to go eat. Osamu asks if he has money from Earth. Yūma says he does, but never used it. He reveals a big wad of cash and begins waving it, saying he only has paper money and a hundred must be enough, catching the attention of nearby people. Osamu, calling him an idiot, runs away with him. Osamu notes to himself that Yūma is very naïve, even if it's his first time in Japan, and that what he did was very dangerous. After they stop running away, Osamu explains to Yūma that he shouldn't show his money in public, as it'll put him in unnecessary danger, which Yūma recognizes. As Osamu reminds him of how people reacted, a thug bumps into Yūma and throws himself to the ground, saying his leg broke. After getting up, he and his partner demand money from Yūma to compensate for his broken leg, but Osamu says he couldn't have broken his leg, which Yūma agrees with. This prompts the thug to punch Osamu to the ground, saying if he said his leg is broken it's because it is, and again demands money from Yūma. Yūma responds by breaking the thug's legs and then giving him compensation money, scaring the thugs away. Osamu, shocked, tells Yūma that he exaggerated, but Yūma says he did what he had to. Yūma says he'll be more careful, as Japan is a dangerous place.

Yūma still wants to eat, so he wants to search for money, but Osamu offers to pay for Yūma's food, and asks Yūma to stay quiet where he is. Yūma then investigates his money, wondering how it works, and is approached by more thugs. Their leader says they need money because their parents are dying due to a disease, but Yūma, knowing they're lying, beats them.

Characters in order of appearance

 * 3 Idiots
 * Tōru Narasaka
 * Shūji Miwa
 * Yōsuke Yoneya
 * Yūma Kuga
 * Osamu Mikumo
 * Ichinose
 * Futatsugi
 * Miyoshi
 * Yotsuya
 * Rad
 * Mole Mod
 * Chika Amatori

Triggers in order of appearance

 * Eaglet
 * Gen'yō Kogetsu
 * Raygust

Adapted From

 * Chapter 2
 * Chapter 3
 * Chapter 4 (until page 5)

Differences Between the Anime and Manga

 * In the original chapter, Tōru does not appear, and the 3 Idiots aren't seen again until the next day, in the school's rooftop.
 * Rads appear sooner in the anime than the manga.