By the end of the Mars mission, the survivors—led by the resilient (with his powerful Japanese horned beetle M.O. Operation) and the tactical genius Michelle K. Davis —return to Earth as heroes. But they bring a ticking time bomb: a sample of the A.E. Virus. The UNE, ever pragmatic and corrupt, sees not a plague but a weapon. They develop a vaccine against the virus, intending to inoculate a select elite. However, the vaccine is flawed. It doesn't just prevent infection—it triggers a latent activation of the virus in anyone who receives it, transforming them into berserk, partially evolved Terraformar-like monsters. This becomes the "Earth-hen" Incident . The Arc’s Central Conflict: A City Under Siege Earth-hen takes place primarily in a sprawling, neo-Tokyo-esque megalopolis called Cocoon City —a sealed, domed metropolis meant to protect the elite from Earth’s ruined atmosphere. The UNE, panicking over the vaccine’s side effects, decides to quarantine and exterminate entire districts of the city where the infected are showing symptoms. Their solution: release a targeted airborne pathogen that will kill all "defective" humans.
Akari Hizamaru saved a city, but he lost his brother. The UNE survived, but its soul curdled further. And in the rain-soaked aftermath, as the survivors bury their dead, one line echoes from the early chapters of Terra Formars , now given a cruel new meaning: terra formars: earth-hen
The survivors of the Annex-1 mission—now public heroes—are horrified. Among the infected are their families, friends, and the very civilians they fought to protect. , in particular, discovers that his adoptive younger brother, Gai , has received the vaccine and is beginning to show signs of Terraformar mutation. By the end of the Mars mission, the
"For the future of mankind."