Sahara the Flower Samurai

Sahara the Flower Samurai is a monthly-published Japanese manga series written and drawn by mangaka, Yuusaku Shibata.

Plot
After the Great War, nearly the entire planet was reduced into a massive desert. Left over from the Great War are mechanical "zombies" roaming the deserts, dissuading most from roaming about without means of flight. This, unfortunately, also leaves most of the world's remaining plant life undiscovered. In fact, the people of the world believe the majority plant life that still exists in the world are puny shrubberies planted in the territory of the insanely wealthy. Flowers have then become extremely rare and worth millions; even the tiniest of them. Products such as bread and water have also become really expensive. Yae Tokiro and her deceased father — a man who, in life, researched plant life — traveled the world together claims to have cross hundreds of miles of land and have found a massive coagulation of plant life, the Valley of the World Tree. It is there, her father told her that "nature was recovering and there's still hope in the world." She desires to return to the World Tree to bury her father's ashes.

Sahara Sanjūrō, a wandering samurai with mysterious powers is able to slay the zombies with his special sword and create plant life and saves Yae from bandits and finds that he too may be looking for the Valley of the World Tree. Thus begins their journey together.