Watch anime episodes online.

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.

Itoshiki Nozomu is the world's most negative person. To his way of thinking, there is no hope or meaning in this existence. Even the three kanji of his name become the two-kanji word zetsubou, "despair", when compressed. What an ironic twist of fate, then, that he becomes teacher to a class containing his precise opposite, the invincibly positive-minded Fuura Kafuka.

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. It's difficult to say who is more surprised and dismayed, but the rules don't allow for second attempts. Louise is stuck with her strange familiar, and he with her.

Planet Zi, a world where warrior bio-machine lifeforms called Zoids live. They are controled by human pilots in a war with the Republic and the Guylos Empire. One day a boy named Van being cased by bandits hides in some old ruins, he finds two pods in a hidden room & opens one to find out its an odd dragon-like Zoid called an Organoid which he names Zeke. Zeke then ressurects an old dead blue Shield Liger Zoid for Van to pilot. When Van opens the 2nd pod a very mysterious girl named Fiona comes out of it. They go on the adventure to find more about her past & to find the Zoid Eve, they meet new friends & they get into some serious problems including the war which they try to stop.

Natural disasters have devastated planet Zi, killing off almost all life. A thousand years later humans have gradually re-established civilization, salvaging ancient Zoids through diving and mining efforts. In a village whose most previous item is a giant sword which they worship as a holy symbol. A teenage boy discovers an ancient Liger-type Zoid while on a deep water salvage operation. Suddenly the village is attacked by skeletal Bio-Zoids intent on stealing a powerful generator located in the village. Our teenage hero awakens the Liger and discovers that the town's sacred sword is the Liger's weapon, together they fight off the mysterious Bio-Zoids. At least for now...

New Century Zero takes place a long time after the events of Zoids: Chaotic Century. Zoids are no longer used for warfare; instead the combative natures of both Zoids and humans are focused and contained by a series of battle-competitions and tournaments, run by the Zoid Battle Commission. The Zoid Battle Commission seems to be a significant power on Planet Zi, fielding a considerable arsenal of armed Zoids, orbital platforms serviced by their own launch facilities as well as orbital based weapons systems. It is not made clear in the series if the Helic Republic and Guylos Empire still exist, although the final battle upon the rusted Ultrasaurus, hinted to be same one in Zoids: Chaotic Century, could suggest neither were left and people had free rein to battle in old battlefields.

R.D. is a delivery boy who works for a company called Mach Storm in order to earn money to search for the legendary Alpha Zoid. A Zoid that he heard rumors about from his dad that he passionately believes in. Mach Storm also doubles as a Zoid Battling team. In R.D.'s first Coliseum Zoid Battle, he encounters a team that can fuse Zoids. R.D. soon discovers that he has a Zoid that can compatably fuse with his Zoid, Liger Zero. After this happens R.D.'s adventure to discover the truth about the Alpha Zoid begins.

Natsume is again meeting new youkai and helping them. A lot of friends join him along the way, he meets others who can also see the spirits and at times they join forces to solve the latest mystery. As always, Nyanko-sensei is there to help Natsume on his quests.

Michiru Kita is a special girl who possesses Shinigami Eyes, which allows her to see a dark ring around a person's neck. This ring symbolizes the person's impending death; once they are marked to die, a gray line, which is invisible to normal people, appears on their neck, and once the ring turns completely black, the person dies. Chika Akatsuki and Shito Tachibana, two boys in her class, both have black rings around their necks, but to her surprise, they are not yet dead. It is revealed that after a tragic accident that was supposed to kill them both, the two boys made a deal with a secret loan office called the Zombie-Loan. In return for keeping them alive, the two have to hunt zombies for the loan office. When Michiru gets involved with them, she finds that her life has just become more complicated.