Since the discovery of Samon Syndrome 30 years ago, thousands of young people have traveled to fantasy worlds, the few returnees managing to keep the special abilities they acquired in those parallel universes. Akatsuki Ousawa, known as the Rogue Hero, discards his peaceful life in the fantasy world Alayzard to face new challenges upon returning to Earth. He comes back with Miu, the daughter of the Demon King he defeated, and is now forced to hide her true identity by having her pose as his little sister. The two soon join Babel, a special school designed for those who have acquired special abilities and magical powers through their journey to a fantasy world. Babel was seemingly founded to train young interdimensional travelers and guide them to the right path for the sake of humanity and themselves, but its true purpose remains unclear to the pseudo-siblings. Will Akatsuki and Miu be able to overcome the hostile, powerful student council and uncover the forces at play behind the scenes?

A young wavemaster, only known by the alias of Tsukasa, wakes up in an MMORPG called The World, with slight amnesia. He does not know what he has previously done before he woke up. In The World, the Crimson Knights suspects him of being a hacker, as he was seen accompanying a tweaked character in the form of a cat. Unable to log out from the game, he wanders around looking for answers, avoiding the knights and other players he meets along the way. As Tsukasa explores The World, he stumbles upon a magical item that takes the form of a guardian, which promises him protection from all harm. Subaru, the leader of the Crimson Knights, along with several other players who became acquainted with Tsukasa, set out to investigate why Tsukasa is unable to log out, and attempt to get to the bottom of the problem before it gets out of hand.

The year is 1866, the twilight of the Tokugawa era. As Japan boldly moves into a new age, one man couldn't possibly care less. That man is Kumosuke Haguregumo, a retired samurai who has since become the town fool. Though he still carries his twin-bladed katana, Kumosuke spends his days smoking, drinking, and womanizing, rarely coming home before dawn. At home, however, wait his wife and two children, Shinnosuke and Ohana, who are constantly troubled by Kumosuke's antics. As Shinnosuke grows older, he begins to understand the world around him. Troubled by his father's reputation, Shinnosuke attempts to live a life of honor, though finding what honor means in a turbulent era is difficult. As Shinnosuke navigates his relationship with his father, countless other warriors struggle to find their place in the ever-changing world.

In 2024, the computer network prevails throughout daily life. Sora Yuuki is a 14-year-old girl. One day, she is invited to an online game The World. After an accident in the game, the real world begins to deform.