World Trigger

World Trigger (ワールドトリガー, Wārudo Torigā) is an ongoing Japanese manga written and illustrated by Daisuke Ashihara that had appeared in Shueisha's  magazine since February 2013. After a two year hiatus, it was announced the manga would instead continue in the monthly magazine .

Background
Ashihara was a large fan of Doraemon, and was inspired by the idea of using future technologies in the present. Before drafting the story, Ashihara created the characters and world. He placed those characters in various roles to see what would work. In the original concept, Yūma was a Border agent, while Osamu was a human who wasn't in Border. Ashihara wanted to create a concept of opposites, so he made Yūma a powerful Neighbor, and Osamu a weak Border agent.

Plot

 * See also: Manga

One day in Mikado City, a gateway to a parallel universe had opened. From it, an outbreak of aliens known as Neighbors wreaked havoc across the city with their own sophisticated technology. Suddenly, a mysterious group of people brought themselves together to repel their attacks. Soon after, Border was revealed to the public, an organization researching Neighbor technology and maintaining a defense system against the Neighbors. Its members are armed with co-opted weapons known as Triggers. Four years later, the city has recovered from initial Neighbor attacks to the point where its civilians have become used to them.

Yūma Kuga is a transfer student from a foreign country admitted to a local school. There, he meets fellow classmate Osamu Mikumo and a group of bullies harassing the two. After fighting off the bullies, a Neighbor appears. One of the bullies is about to get eaten, but Osamu (who is actually a member of Border) activates his Trigger, but fails to defeat the Neighbor, leaving Yūma to activate his own Trigger and defeat it successfully. Yūma reveals he isn't part of Border, as his Trigger was a memento of his dead father who had wanted him to move to Japan to join Border. He also reveals his father wasn't part of Border either, and that he actually transferred from the alternate dimension where Neighbors come from, the Neighborhood. He had come to find his father's acquaintance.

Following this revelation, a Rad Infestation takes place where Rads were hiding in various locations within the city (outside of the Danger Zone) and opened gates for Trion Solders to pour in. One of these places was the school, where Osamu failed to stop them, but Yūma used his Trigger and Osamu's to defeat them. Because using training Triggers outside of Border was forbidden, Osamu is evaluated for punishment. Along the way, an Ilgar attacks the city, and Yūma is compelled to use his Trigger in secret to save civilians, alerting Border of his existence. He helps solve the Rad mystery. With Osamu's suspicious defeat of the Marmod that attacked the school, Miwa Squad begins monitoring him. At the same time, Osamu introduces Chika Amatori to Yūma, a girl who attracts Trion Soldiers. Yūma reveals this is because of her abnormally large Trion amount. Miwa Squad, having surveyed Osamu, discover Yūma's identity. Yūma easily defeats them in a battle with his Black Trigger, so Kido orders the capture of the Trigger.

Yūichi Jin, an S-Rank agent of Border affiliated with Tamakoma Branch, invites Yūma to join Border. Yūma discovers that his father's acquaintance, Sōichi Mogami had passed away by becoming Jin's Black Trigger Fūjin, leaving him with hardly any motivation to remain on Earth. Replica reveals Yūma's other goal to Osamu, so Osamu has Yūma join him in a team to recover Rinji Amatori and Aoba Harukawa. Yūma agrees. While being introduced to Tamakoma Branch, Jin engages with the assault force assembled by Kido which consists of Tachikawa Squad, Fuyushima Squad, Kazama Squad, and Miwa Squad. With the help of Arashiyama Squad, he defeats them. To ensure Yūma's safe enlistment into Border, he gives up Fūjin.

Yūma and Chika enlist in Border and make a flashy debut. Even Osamu becomes famous for tying with Sōya Kazama, the No. 2 Attacker. However, a new threat emerges: a Second Large-Scale Invasion. The Neighbor nation, Aftokrator, sends 6 agents to capture C-Rank agents and find someone with high trion levels to sustain their planet. During this invasion, Jin predicts that Osamu may die. A new Trion Soldier, a Rabbit, is deployed: capable of capturing agents and more powerful than the average B-rank combatant. With the arrival of humanoid Neighbors and Black Triggers, Border is met with superior technology, but using teamwork, they defeat their adversaries. Osamu is left severely wounded, but survives. One of the Neighbors, Hyuse, is left behind, while another, Enedra, is killed by his comrade.

Osamu's troubles are not over, though, as several C-Rank trainees were kidnapped; it is speculated that his being defeated without Bail Out in front of the enemy Trion Soldier led to them learning of the trainees' lack of Bail Out. However, he manages to deflect this attention to the prospect of entering the Neighborhood and recovering the kidnapped personally. Following this, Border experiences a much higher application rate. At this time, the B-Rank Rank Battles begin. Yūma and Chika rise to B-Rank, forming Tamakoma Second with Osamu. They participate in the Rank Battles and face various opponents. They win their first 3 battles with relative ease. However, their fourth match is a huge loss as they challenge the top B-Rank Squads. The captain of the B-Rank #1 Squad, Masataka Ninomiya, reveals that he has information regarding Rinji's disappearance, but refuses disclosure until Tamakoma Second has qualified for the away mission, deeming it useless to reveal otherwise.

Aftokrator orders its vassal nations to cripple Border's offensive power. Galopoula sends its Expedition Force while Rodochroun send Trion Soldiers. The objective is to destroy the Expedition Ship. Border manages to repel the invaders, and in the process, Hyuse learns that Galopoula received orders to disregard him, sensing that something dire was going on in Aftokrator.

Following Osamu's negotiation with Kido, Hyuse joins Tamakoma Second to help them join the Expedition Force that will journey to the Neighborhood, as he has similar goals. At the end of the Rank Wars season, Osamu's team reaches B-rank #2. But before the away mission comes the Expedition Selection Exam, a series of tests spanning several days in order to evaluate the most qualified applicants...

Main Characters

 * See also: Characters

Settings

 * Mikado City