Chrome Shelled Regios is a futuristic fantasy series set in a post-apocalyptic world where humanity has been forced to live in mobile cities, known as Regios, to escape the contamination and monstrous creatures outside. However, no specific information about specific episodes or a detailed synopsis for Season 1, episode 13, titled "The Sentiment That Lies in the Barrel of a Gun," exists in my database. Therefore, I am unable to provide the description you requested. If you'd like, I can offer a general overview of the show's themes and narrative style, but I cannot craft a detailed episode description without accurate source material.