In the year 2005, a computer virus called 'Pluto Kiss' completely shuts down and restricts the global internet network of the world. In 2007, after extensive rescinding of the network, they create and release an online Network Game (MMORPG) called 'The World'. The main character, Tsukasa, a mysterious girl playing a boy character, cannot log out of The World, for some unknown reason. Tsukasa has led a very bad life and tries to escape reality. He also found a way to bypass the game's rules, which angers the admins because they can't catch him or ban him from the game. A hacked character in a cat form enfluences how Tsukasa thinks and acts, and a bounty is placed on him. Other players meet Tsukasa and try to get him to open himself to them and explain what happened.

In the year AC (After Colony) 195, earthlings have formed five separate colonies independent from the mother planet. A central government called the Alliance is established to supposedly ensure peace on earth and the colonies. But the Alliance does not seem genuinely interested in the general welfare of the people, and its rule is not unopposed. As a response to the situation, five scientists from the five colonies developed a new type of robotic fighter known as a Gundam -- created from a powerful metal called Gundanium Alloy. The Gundams are piloted by five young men who share a common goal -- to end the Alliance rule. Ironically, the pilots don't know each other... and only when their paths cross do they begin to see the whole picture.