Story:
In a post-apocalyptic polluted earth overrun with mutated beasts called Filth Monsters (Contaminoids in Funimation's translation), humanity is forced to live in large mobile cities called Regios and learn to use weapons called DITE and harness the power of Kei to defend themselves. In the Academy City of Zuellni, Layfon Alseif is hoping to start a new life without Martial/Military arts and forget his past. However, his past has caught the attention of Kalian Loss, the Student Council President and Nina Antalk, a Military Arts student and Captain of the 17th Platoon, who instantly recognizes his abilities and decides he's the perfect candidate to join her group. The series follow Layfon's life in Zuellni and occasionally has flash backs of his life in Glendan.

Info:
Chrome Shelled Regios (鋼殻のレギオス) is a Japanese light novel series by Shūsuke Amagi, with illustrations by Miyū.
There is an anime and manga adaptation, as well as spin-off series.

Light Novel list:
Chrome Shelled Regios - 20 volumes
Legend of Regios - A 3-volume, science-fiction light-novel series that is set in the past world of the Chrome Shelled Regios series.
Regios Crusade - A spin-off series.

An anime adaptation produced by Zexcs aired on January 11, 2009 to June 20, 2009 and is licensed in North America by Funimation Entertainment. The 24 episodes anime adaptation started airing in January 2009 and is produced by Zexcs. The anime itself is a reinterpretation of the manga, featuring the same characters with an expanded group of characters. At the season finale, many of the plots within the story remain unresolved, suggesting a possible continuation of the series, but there has yet to be confirmation of a second season.

*The Legend of Regios side-story takes place in the same world, but during a time of the past. In the anime, all of the characters speak in English with a Japanese accent, probably as a result of being voiced over by Japanese seiyu.

Manga list:
A list of mangas from Chrome Shelled Regios which are mostly ongoing.
Chrome Shelled Regios
Chrome Shelled Regios: Missing Mail (Author:Kiyose Nodoka)
Chrome Shelled Regios: 4-panel mangas (Author:Futaba Masumi)
- 4 koma Felli's Poem
- 4 koma Felli's Poem Plus
Chrome Shelled Regios: Secret Side (Author:Watari)
This is an extra version that is recognized by the original author and fans alike. In its brief synopsis, the story explores the main understanding of humanity's survival in Regios cities, as the main protagonist Layfon, searches for the significance of his existence and faces his worst enemy. We can also expect to catch a glimpse of a new side to our hero.

Characters info
Source: Wikipedia, Japanese sites