Garan no Hime

A world where eternal creatures known as "Monotsuki" are common and machine civilization has vanished. Born in an isolated village, Isana encounters a memory-impaired mechanic who resembles her sister, who ought to have vanished in the ruins she entered. Isana gives the artificial figure the name "Hime" (princess), convinced that "My sister is alive," and they embark on a quest to locate her.