Shuumatsu Sekai no Hakoiri Musume

Long after the fall of humanity, the world lies in ruin. Factions of autonomous war machines, monstrous biological weapons, and other horrors of a bygone era battle it out in the remains of the society that created them, their conflicts endless and seemingly meaningless—until, that is, a machine finds its own meaning in the form of a human child. That machine, Humanoid Mobile Weapons Unit Number Ten, develops a fiercely protective bond with the child, and soon the two of them set out on a journey together. Their mission: to search for other human survivors, to deliver the child to her people...and to enjoy the trip for all they’re worth!

(Source: J-Novel Club)