In Martian colony Fourth Tokyo lies a classroom of Kirishina Corporation's brightest minds spearheading aerospace development: A-TEC, led by genius engineer Kaito Sera, eagerly anticipating the arrival of their newest member. It soon becomes clear, however, that the transfer student is hardly ordinary—Nagisa Kiryuu, newly appointed chief of A-TEC and the younger brother of the corporation's CEO, is sent to shut the program down. To keep the classroom alive, Kaito and his students desperately work to develop a successor to their most powerful rocket, the X-2; meanwhile, Nagisa climbs the corporate ladder in pursuit of his own mission. In spite of this, their separate battles soon reveal that much more is going on in Kirishina Corporation than meets the eye. Classroom☆Crisis follows Kaito and Nagisa, as well as Kaito's younger sister Mizuki and A-TEC's test pilot Iris Shirasaki, in a story of intrigue, political warfare, and, against all odds, romance. As Nagisa and A-TEC are dragged further and further into Kirishina Corporation's conspiracies, friendships grow and pasts are unveiled as they fight to avert their classroom crisis. [Written by MAL Rewrite]

Tanya Degurechaff is a soldier who has the appearance of an innocent young girl. But behind her cute facade lies the soul of a ruthless salaryman who challenged "Being X"—the self-proclaimed God who reincarnated the man into an industrial world of magic. By doing this, Being X hopes to prove that, if the situation were dire enough, even a non-believer like this man would pray for God's help. Opposing Being X's desires to make her suffer, Tanya enlists in the military with the hope of living a peaceful life. She manages to impress the higher-ups with her aptitude for war, swiftly rising through the ranks. However, her country soon participates in the ongoing world war, quickly crushing her dream. In an attempt to return to her calm she starts using any merciless means to obliterate her opponents. Thus begins the saga of Tanya the Evil and the Empire as they seek world domination.

After overcoming various tumultuous events, mercenary sergeant Sousuke Sagara of Mithril and "Whispered" school girl Kaname Chidori return to their normal high school lives. Sousuke continues his efforts to assimilate with the civilian population and manage his mission at the same time, while Kaname attempts to support his endeavors (even though his antics often drive her up a wall). However, as their lives calm, new problems begin to appear. The appearance of an independent terrorist organization known as Amalgam and internal conflicts within Mithril threaten to wreak unity into a series of failures and betrayals. And new, powerful Arm Slave models only worsen the situation when the world's peace is at stake. As Kaname and Sousuke face their own inner battles amidst life-threatening fights, will they be able to make the right choices and change their future? [Written by MAL Rewrite]

Three years into the war, Mahito Maki loses his mother in a tragic fire at the hospital. Shortly thereafter, his father marries Natsuko, the younger sister of Mahito's mother. They take Mahito out of Tokyo to seek refuge in his late mother's rural family home. There, Mahito is constantly taunted by a strange gray heron, who seems to have taken an interest in him. Unable to come to terms with his loss and struggling to adjust to a new life in an unfamiliar place, the boy is shocked to discover that Natsuko is pregnant. To make matters worse, the pesky heron can speak—and claims that Mahito's mother is still alive. Luring him into a mysterious tower near the residence, the heron says that Mahito can save her from death, but the boy is not easily swayed. When Natsuko disappears one day, however, Mahito watches her walk into the tower and becomes compelled to venture in to rescue her. He soon finds himself falling into another world below his, where life and death seem to be entwined. As he navigates through this foreign realm to find Natsuko, Mahito must understand what it means to live if he wants to safely return home.