Young teenage girl Roue lives a peaceful life with her "uncle", a gear named Zett. She spends her days exploring the ruins of the old world, destroyed by World War III two hundred years ago. During one of those explorations, she finds a strange cylindrical gear who calls himself Chrome, who for some reason doesn't have a "base program", which determines a gear's main purpose. Chrome may have to find that purpose himself in his new life with Roue and Zett...

Officially published:
[*]In english free on MangaPlus (See "Official English" link below)
[*]In spanish free on [url=https://mangaplus.shueisha.co.jp/titles/200028]MangaPlus[/url]
[*]In french by [url=http://www.ki-oon.com/mangas/tomes-1187-heart-gear.html]Ki-oon[/url]