In the future, a meteor crashes into Earth and brings with it a virulent form of life. This virus is known as M34 and attacks humans, turning them into vicious monsters. Most of the human population is wiped out, thus government agencies are formed to fight the virus. One of the groups, NOA, inserts nanomachines into the bodies of its soldiers; these machines allow them to transform and fight off the infected. Unfortunately, the virus mutates and becomes too strong for NOA to handle. Now the fate of the world rests in the hands of 16-year-old girl with the power to defeat the virus.

Nozomu Itoshiki is still the bizarre teacher of the even stranger Class 2-H. He attempts to teach his students the negative aspects of the world and society, only to have each circumstance thrown at his face whenever he tries. With more students and friends than before, Zetsubo-sensei's life bcomes harder and crazier than ever before

Takamine Kiyomaro, a depressed don't-care-about-the-world guy, was suddenly given a little demon named Gash Bell to take care of. Little does he know that Gash is embroiled into an intense fight to see who is the ruler of the demon world. All of the demons have to pick a master on Earth and duke it out with other demons until one survives. Needless to say, Kiyomaro becomes Gash's master, and through their many battles, Kiyomaro learns the importance of friendship and courage.

Kyo, an avid swimmer tries his best to keep the high school swimming club going, which is pretty hard when he's the only member. Facing the prospect of the club being closed by the student council, he tries to enlist beautiful Misaki to act in a promo video, shot by his good friend Ryoko, in a bid to start a recruitment drive. She agrees but only if he pilots a mecha under the wing of Celebrum, a resistance organisation fighting to destroy Deutera Areas formed on Earth by the aliens Gards-orm. He agrees but finds it all strangely familiar as if he's done it before....

Meet Louise, a budding magician. The students at the Tristein Academy call her "Zero Louise", due to her current record of zero successes with magic. In fact, her magic tends to go spectacularly wrong. Now, as an important test of her aptitude for magic, she must summon a familiar to be her servant. At this critical moment, she summons up all her magic and wishes for a familiar that is "devoted, beautiful and powerful", and gets... Hiraga Saito, an ordinary Japanese boy.

Following Saito's heroic actions in the War with Albion in season two, Saito & Louise return to Tristain, only to have the runes which bind Saito & Louise disappear. Saito & Louise struggle with a relationship no longer defined as Master & Familiar, as they search for an Elf who has the power to restore the dead to life, and may hold the key to understanding Saito's loss of the Gandalfr's power.

This sequel is a continuation of the previous season, not long after the war. Louise and Saito seemingly getting along now since she knows that he had given up his only chance to return to Tokyo for her. The story continues as Louise begins to use Void Magic from a mysterious secret book she had recieved from her majesty Henrietta, while a new villain has appeared in town causing trouble.

In the not-so-distant future, people think it natural that Espers exist. This does not mean that no conflict occurs between Espers and normal people. Young, scientific genius Minamoto Koichi is assigned to be a watchdog of level 7 (the highest rank) Esper girls: Kaoru, Aoi, and Shiho. Despite their cuteness, they have a little problem…

Aizawa Ayumu is a young boy, who is sent to a small town called Tana to live with his father for a while. Even though he doesn't want to go, he agrees to do so when his mother offers him a mountain bike. Ayumu used to live in Tana before, and now his memories of the time are shrouded in mystery - apparently something happened when he was a child. Enter Miku, a young girl who knows more than she tells, weird glowing lights floating around, reflections of UFOish objects in the eyes of cats and dogs, a nosy female announcer, a forest with a mysterious past, and a weird boy called Wakkun, who wears the clothes Ayumu used to when he was a child, and you get the world of Zettai Shonen, where mysteries remain mysteries amidst a slow, normal, everyday life.

Mirai, an improved Kongou-class Aegis guided missile destroyer, is one of the newest and most advanced ships in the entire Japanese Self-Defense Force (SDF). Her crew, also one of the newest, is lead by Capt. Umezu Saburo and Executive Officer Kadomatsu Yosuke. While running scheduled training exercises one day, Mirai encounters a fierce storm that throws their navigation systems into temporary disarray.