
As a rookie Neuron officer newly recruited into the team, the protagonist and their Legion partners must work together to investigate, solve cases, fight chimeras, and save humanity itself. Only a few people have the potential to wield the Legion effectively as officers of Neuron, and the protagonist along with their twin sibling Akira Howard are two police officers with such qualities. Neuron officers employ the use of the Legion, a special living weapon created by capturing a chimera, neutralizing it with armor, and neurologically syncing it to a human operator through the eponymous "Astral Chain".

The existence of the chimeras was kept secret from the residents of the Ark while a special police task force known as Neuron was established specifically to counter the extradimensional threat. The survivors took refuge in a massive artificial island metropolis known as the Ark, where peace was enjoyed for ten years before gates finally began appearing in the Ark as well, bringing invisible creatures known as chimeras from the world behind the gates - the Astral Plane. Within six months of the gates' appearance, 90% of all land on Earth was rendered uninhabitable.

Smaller gates began appearing throughout all continents, causing global collapse as pollution from the gates known as Red Matter began corrupting the people and land of Earth in a process known as redshift.
#Astral chain akira series#
In 2043, a meteor impact with the Earth caused a mysterious wormhole known as a gate to form, triggering an apocalyptic series of events.
