The Brazilian city of Rio de Janeiro is slowly engulfing the surrounding jungle and animals that live there. Above Rio's chaotic streets, a group of tiny marmosets have left the trees and, like 'free runners', use the city's power-lines to scour the city for food and keep one step ahead of people, cars and feral cats. Far from Brazil is the futuristic neon metropolis of Tokyo. Here, a very different cast of characters is learning how to survive in the city. A formidable looking rhinoceros beetle - for his size the strongest animal in the world - is forced to fight other beetles for money.