Waza no Tabibito

Humans discovered a perfect energy source called "Patia," which brought self-sufficiency in food and fuel to everyone worldwide. Trade and transportation diminished, and civilization's progress halted. Now, genetically modified plants cover almost all the lands on earth, obstructing travelers. Cient, the leader of a fortress city, sets out on a trip to excavate the lost technology "Patia" with his daughter Ruri. When Ruri gets separated from her father, a giant humanoid weapon from the old age attacks her. Ruri is saved by a girl named Tekuni, who is traveling around the world training as a "Wazabito" fighter.