In Mikado City (280 000 inhabitants), a "gate" to another world is opened unexpectedly one day. Creatures called "Neighbors" begin appearing from it, many people are scared of them because Earth's arms do not work against them, but a cryptic group begins fighting off the Neighbors. They, the "Border" protection bureau, develop a defense system from the Neighbors. Now, since that time, whatever the Neighbors still appearing in the gates, individuals of Mikado City were dwelling generally. Yumother Kuga, a humanoid Neighbor, comes to Mikado City, where he fulfills a Border representative, Osamu Mikumo four plus a half years following the gate is opened for the very first time.
Osamu Mikumo is a character in among the key protagonists plus the anime and manga show World Trigger. He could be a B Class Shooter and captain of Mikumo Unit.
Yumother Kuga is a character in among the key protagonists plus the anime and manga show World Trigger. He could be a Bclass Attacker and member of Mikumo Unit. He's a Neighbor.
Yuichi Jin is an A Class (previously S Class) member of Border, and part of Tamakoma Branch. He's among the primary protagonists of World Trigger Manga.
Chika Amatori is a character in among the key protagonists plus the anime and manga show World Trigger. She's a B Class Sniper and member of Mikumo Unit.
Replica is Yuma the guard of Kuga. This is a self described "multi-task Trion Warrior".
Daisuke Ashihara wrote and illustrated the manga. Individual chapters have been serialized in Weekly Shunen Jump since February 2013, and therefore are rolled up into tankubon volumes published by Shueisha. As of September 2015, a dozen volumes are released in Japan. The set has been permitted by Viz Media