Since the discovery of "Samon Syndrome" 30 years ago, thousands of young people have traveled to fantasy worlds, the few returnees managing to keep the special abilities they acquired in those parallel universes. Akatsuki Ousawa, known as the "Rogue Hero," discards his peaceful life in the fantasy world Alayzard to face new challenges upon returning to Earth. He comes back with Miu, the daughter of the Demon King he defeated, and is now forced to hide her true identity by having her pose as his little sister. The two soon join Babel, a special school designed for those who have acquired special abilities and magical powers through their journey to a fantasy world. Babel was seemingly founded to train young interdimensional travelers and "guide them to the right path for the sake of humanity and themselves," but its true purpose remains unclear to the pseudo-siblings. Will Akatsuki and Miu be able to overcome the hostile, powerful student council and uncover the forces at play behind the scenes? [Written by MAL Rewrite]

Once upon a time, a race known as the Shadow Angels attacked Earth to harvest the life force of all those who inhabited the planet. Thanks to some outrageous miracle, the Shadow Angels went dormant, and humanity was able to live another 12,000 years without fearing their presence. But 11 years after a catastrophe dubbed the Holy Genesis brought ruin to the Earth, the Shadow Angels were stirred from their slumber and resumed the attacks once more. To give humanity somewhat of a chance, an organization known as DEAVA was formed, and use of a robotic weapon named Aquarion has been authorized. In order for the Aquarion to be brought to full power, three pilots must combine their hearts, bodies, and souls into one—a feat few can hope to accomplish. Thus, the search for so-called 'Element Users' was prioritised, hoping to ensure humanity's future. Sousei no Aquarion follows the story of Apollo, a near-feral young man brought up in poverty, who is believed to be a legendary hero reincarnated. After his best friend is taken by the Shadow Angels, Apollo chooses to become an Aquarion pilot. Will he be able to turn the tides of the war, and free humanity from the threat of the Shadow Angels for once and for all?

It's the Taisho era—a time filled with the scent of romance, and people's hearts are still filled with compassion. Unzen, Sukayu, Unohana, Oshamanbe, and Aso are all ordinary (?) male students at Mayunan High School, who spend their days lazing around in the clubroom of the "do-nothing club" Earth Defense Club, and live together in the Kurodama dormitory. One day, while the five are taking a morning bath at the Kurodama dormitory, they notice something slimy moving in the bathtub. When they finally manage to catch it, it turns out to be a talking Pallas's cat named Nuru! Nuru has come from the distant future with a serious mission to inform them that the Earth is facing an impending threat of destruction. While he says he wants to protect the Earth, he says he's only come to warn them of the crisis, and that it's up to the five of them to decide whether or not they want to fight for the Earth... Isn't this just an attempt to dodge responsibility? The Defense Club members are suspicious. "If either is fine with you, I'll do it! That's more fashionable!" Unzen enthusiastically says. The five decide to fight with free will, and Nuru transforms them into the Fashionable Romantic Troupe using cat science. Meanwhile, a mysterious trio called the Bankara New Elite Squad are scheming in the shadows. They are plotting to take over the Earth.