Ever since the release of the innovative NerveGear, gamers from all around the globe have been given the opportunity to experience a completely immersive virtual reality. Sword Art Online (SAO), one of the most recent games on the console, offers a gateway into the wondrous world of Aincrad, a vivid, medieval landscape where users can do anything within the limits of imagination. With the release of this worldwide sensation, gaming has never felt more lifelike. However, the idyllic fantasy rapidly becomes a brutal nightmare when SAO's creator traps thousands of players inside the game. The log-out function has been removed, with the only method of escape involving beating all of Aincrad's one hundred increasingly difficult levels. Adding to the struggle, any in-game death becomes permanent, ending the player's life in the real world. While Kazuto Kirito Kirigaya was fortunate enough to be a beta-tester for the game, he quickly finds that despite his advantages, he cannot overcome SAO's challenges alone. Teaming up with Asuna Yuuki and other talented players, Kirito makes an effort to face the seemingly insurmountable trials head-on. But with difficult bosses and threatening dark cults impeding his progress, Kirito finds that such tasks are much easier said than done.

A year after escaping Sword Art Online, Kazuto Kirigaya has been settling back into the real world. However, his peace is short-lived as a new incident occurs in a game called Gun Gale Online, where a player by the name of Death Gun appears to be killing people in the real world by shooting them in-game. Approached by officials to assist in investigating the murders, Kazuto assumes his persona of Kirito once again and logs into Gun Gale Online, intent on stopping the killer. Once inside, Kirito meets Sinon, a highly skilled sniper afflicted by a traumatic past. She is soon dragged in his chase after Death Gun, and together they enter the Bullet of Bullets, a tournament where their target is sure to appear. Uncertain of Death Gun's real powers, Kirito and Sinon race to stop him before he has the chance to claim another life. Not everything goes smoothly, however, as scars from the past impede their progress. In a high-stakes game where the next victim could easily be one of them, Kirito puts his life on the line in the virtual world once more.

Yukiteru Amano is a shy middle schooler who regularly keeps track of what he does in his daily life by writing down all of his activities on his phone—a digital diary. Despite having no friends at school, Yukiteru is frequently seen talking to his supposedly imaginary friends Deus Ex Machina, the god of time and space; and Deus' servant, Mur Mur. One day, Yukiteru wakes up and discovers that certain events of his day are preemptively displayed on his cellphone. While initially dismissing it as a coincidence, he slowly realizes that the incidents written in his phone actually take place in the near future. After spending the day benefiting from this new asset, Yukiteru learns that his classmate Yuno Gasai possesses a similar diary. As the two team up to defeat an odd pursuer and head back to their respective homes, Deus Ex Machina explains that they—alongside 10 other contestants—have been drawn into a survival game whose victor will become the deity's successor. With no other options, Yukiteru and Yuno must use their cellphones—now called Future Diaries—to survive this unforgiving battle royale.

In class 3-3 of Yomiyama North Junior High, transfer student Kouichi Sakakibara makes his return after taking a sick leave for the first month of school. Among his new classmates, he is inexplicably drawn toward Mei Misaki—a reserved girl with an eyepatch whom he met in the hospital during his absence. But none of his classmates acknowledge her existence; they warn him not to acquaint himself with things that do not exist. Against their words of caution, Kouichi befriends Mei—soon learning of the sinister truth behind his friends' apprehension. The ominous rumors revolve around a former student of the class 3-3. However, no one will share the full details of the grim event with Kouichi. Engrossed in the curse that plagues his class, Kouichi sets out to discover its connection to his new friend. As a series of tragedies arise around them, it is now up to Kouichi, Mei, and their classmates to unravel the eerie mystery—but doing so will come at a hefty price.