Princess of Cathedral summary:
In a world where mechanical civilization has perished, immortal monsters called "Monotsuki" are rampant. Isana, a girl born in a remote village, wanders into a ruin where she meets a mechanical man who looks just like her sister who disappeared and has no memories. Convinced that her sister is alive, Isana gives the mechanical man the name Hime and together they set off on a journey to find her.