One thousand years after the Giant Warriors caused an apocalyptic event known as the seven days of fire, humans are living in constant fear of the Toxic Jungle. This ever-spreading forest is filled with poisonous plants and gigantic monstrous insects; even the very air is deadly. Nausicaa is the kind and wise princess of a small, peaceful country known as the Valley of the Wind, which has so far avoided the spread of the forest. One night a large airship containing one of the Giant Warriors crashes into the valley. The following day soldiers from the powerful nation of Tolmekia invade the Valley of the Wind to reclaim and revive the warrior. As the only one who truly believes that there is a way for humans to live alongside the insects, Nausicaa must find a way to stop the war that now threatens her people and protect the Toxic Jungle before the Tolmekians burn it to the ground.
Akiyuki lives on post-war Sentan Island, always rushing between the demands of his separated parents and his friends at school. But his carefree days come abruptly to an end when his school bus suffers an explosion, the first attack to plunge Sentan back into war. Akiyuki lives to find himself turned into a Xam'd, a mysterious creature, by the suspected cause of the explosion. Engulfed by Xam'd, Akiyuki is eventually saved by a red-haired girl, Nakiami, only to find himself torn away from those he loves. Now he must work to control and understand the creature within him, all while searching for his family and friends in a world steeped in the secrets and chaos of war.
The first five minutes of the very first episode of Xam'd gave me an overwhelming Nausicaa vibe, and the feeling really hasn't diminished with successive episodes. I guess the most obvious similarity is that both feature a heroine who flies a single-person light aircraft and grows things in jars and is tough yet deeply compassionate, to the point of defending or weeping over creatures others would think of as monsters. Also, there's lots of airships and goopy stuff and morally complex war stuff and a cute animal. Basically, if you like Nausicaa, be sure to check out Xam'd. If you like Xam'd and you've never seen Nausicaa... have you been living under a rock? It's a classic!