After the termination of the incredibly popular virtual reality MMORPG The World, a new version of the game—The World R:2—is brought online. On his first day in the game, newcomer Haseo thinks he has made some friends to quest with. However, as if mocking his sentiments, they kill his character just for fun. Luckily, he is saved by a mysterious, one-armed player named Ovan who offers to show him around The World. Alongside Ovan and his cleric friend Shino, Haseo enjoys a wonderful first year in the game. But this peaceful life is shattered when Shino's character is killed by a familiar figure notoriously known as Tri-Edge, whose victims have all fallen into comas in the real world. In a fit of rage, Haseo vows to find the elusive Tri-Edge and kill him. Taking place during Haseo's first year in The World, .hack//Roots explores the friendships Haseo built in the game before Tri-Edge ripped them away.

In the game, the player takes the role of an unnamed former little senior league baseball ace who lost his or her baseball career after suffering an unspecified injury. The character moves to his or her grandmother's hometown and enrolls in the local high school, resolved never to enter the world of baseball again. When the character meets Tsubasa Arihara, he or she is persuaded to be the manager of the school's baseball team, and to take the team to the high school nationals at Koshien. (Source: ANN)

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.

A hundred years after catastrophic shifts in tectonic plates caused most of its area to submerge, Japan now thrives as a maritime nation. High functioning cities line the coasts of Japan, and well developed sea routes are defended by specialized naval ships. The marine industry is flourishing, and young girls are eager to join the Blue Mermaids—highly skilled women who devote their lives to protecting the seas. After some time apart, childhood friends Akeno Misaki and Moeka China are reunited at Yokosuka Girls' Marine High School. Here they are joined by others who share their dream of becoming Blue Mermaids. Soon, training exercises commence, with Akeno and Moeka being put in charge of their own ships and crew. Everything is progressing smoothly for Akeno as she settles into her role as captain and builds camaraderie between her fellow crew members aboard the Harekaze, a destroyer ship. However, unexpected engine and navigation failures soon leave their ship stranded and the crew in danger. High School Fleet follows the Harekaze's valiant crew as they navigate treacherous waters and other obstacles on their quest to become fully fledged Blue Mermaids.