Naota Nandaba is an ordinary sixth grader living in a city where nothing amazing ever seems to happen. After his brother Tasuku leaves town to play baseball in America, Naota takes it upon himself to look after everything Tasuku left behind—from his top bunk bed to his ex-girlfriend Mamimi Samejima, who hasn't stopped clinging to Naota since Tasuku left. Little does Naota know, however, that his mundane existence is on the verge of being changed forever: enter Haruko Haruhara, a Vespa-riding, bass guitar-wielding, pink-haired psychopath whose first encounter with Naota leaves him with tire tracks on his back and a giant horn on his head. Though all he wants is some peace and quiet, when Haruko takes up residence at his parents' home, Naota finds himself dragged into the heart of the greatest battle for supremacy that Earth—and quite possibly the entire universe—has ever seen.

Carefree high school senior Yuki Takeya every day looks forward to the School Living Club. Consisting of the president Yuuri Wakasa, the athletic Kurumi Ebisuzawa, the mature Miki Naoki, the supervising teacher Megumi Sakura, and club dog Taroumaru, the club prides itself on making the most of life at school. There is only one rule the club members have to follow: all members must live their entire lives within school grounds. Gakkougurashi! follows the adventures of the School Living Club as they promote independence and self-determination through their lively time residing at Megurigaoka Private High School.

Six years have passed since Rion discovered his own identity as an artificial being, yet succeeded in destroying the genocidal Mother Computer, Dorothy, before perishing himself. Now reactivated by Lilia, Rion awakens to find that Dorothy managed to execute one final catastrophic program, rendering a new evil crew to finish her goal of human annihilation. It is a fully 3D CGI animated OVA based on the hit PlayStation game, called Galerians, released in August, 1999. (Source: AniDB)

Despite having seemingly returned to their normal lives, Kei Kurono, Masaru Katou, and Kei Kishimoto are forced back into the lethal game after Gantz's recent activity. The black sphere continues to summon recently deceased people to fight alien invaders. And having survived the two previous encounters, the trio are more than prepared for the upcoming missions. As they progress through the tournament's stages, the three proceed in their attempt to earn 100 points, which is said to be the only way to leave the parallel dimension for good. However, with the constant onslaught of alien invaders and the threat of imminent death, they must first focus on the task at hand—immediate survival.