High school student Kaname Sudou receives an invitation from a classmate to play Darwin's Game, a mobile game he has never heard of. However, as soon as he opens the application, a green snake suddenly pops out from his phone screen and bites his neck, leaving him unconscious. Waking up in the infirmary without any signs of a snake bite, he is told by the school to take the rest of the day off. Although he is puzzled by what has happened, he dismisses the surreal experience as a hallucination and boards the train home. Unfortunately, his curiosity gets the better of him and he uses the application once again. As the application appears to be just like any other battle game, Kaname breathes out a sigh of relief and decides to start his first match. However, the pleasant surprise is short-lived, as his in-game opponent unexpectedly appears right in front of him and attempts to hunt him down with a knife. As he desperately runs for his life, Kaname puts two and two together and realizes that Darwin's Game is not an ordinary game, but rather, it's a brutal fight for survival.

The disappearance of the Spearhead Squadron beyond the horizon does little to hide the intensity of the Republic of San Magnolia's endless propaganda. Vladilena Milizé continues to operate as Handler One, the commander of yet another dehumanized 86th faction's squadron in the continuous war against the Legion. On the Western Front, Shinei Nouzen and his squad are quarantined in a military base controlled by the Federal Republic of Giad, formerly known as the Giadian Empire. The newly-established government grants the saved Eighty-Six full citizenship and freedom. Housed by the president Ernst Zimmerman himself, the group meets his adoptive daughter and the last Empress, Augusta Frederica Adel-Adler. However, within the calm of this tender society, Shinei and his team feel that their purpose is on the battlefield. Before long, they are once again in the midst of the Legion's onslaught as a part of the Federacy's Nordlicht Squadron, accompanied by Augusta Frederica. But, as history repeats itself, they realize that no matter the side, death and pain on the front lines are the only comfort they know.

The world's greatest assassin had sworn lifelong allegiance to the organization that raised him. However, despite his loyalty, that very same organization takes action to silence him, ultimately leading to his demise. Drowning in frustration and regrets he can no longer suppress, he finds himself in an audience with a goddess attracted by his exceptional skills. The goddess offers him reincarnation into a magnificent world of swords and magic so he can perform a crucial mission: prevent that world's destruction by slaying its hero. Accepting the goddess' request, he is reborn as Lugh Tuatha Dé, the son of a noble family of assassins serving the Alvan Kingdom. Under the guidance of his father, Lugh learns new assassination techniques that significantly differ from the cold-blooded and unsympathetic killing style of his previous life. Furthermore, his other talents bloom, allowing him to meet new allies and acquaintances. Even so, Lugh knows that his efforts are far from adequate, because a monumental adversary such as the hero can only be defeated with perfection.

With her ability to read minds, Anya Forger is the only one who knows the true identities of her unconventional family. Her pretend father Loid operates as an elite spy code-named Twilight; her mother Yor kills on demand as the assassin Thorn Princess; and their dog, Bond, possesses the gift of precognition. Although they hide the truth from each other, this pretense of a perfectly ordinary family provides Anya with the genuine love and warmth that she longed for as an orphan. Operation Strix—Loid's special mission to avoid potential war by gathering vital information and getting close to the powerful political figure, Donovan Desmond—is only possible if Anya plays her part right. She can either excel academically and become an Imperial Scholar at her prestigious school or make friends with Donovan's son, Damian. Neither is exactly easy, but with her adventurous attitude, Anya throws herself wholeheartedly into her mission as a Forger—all for the sake of international peace.