Only some children in the orphanage are lucky enough to have a patron—and a small, curious child named Mori starts receiving gifts one day. Mori does not speak, but he listens and enjoys the company of his friend, Rowena, who tells him everything he needs to know. But once Rowena disappears in the warm embrace of her mother, Mori realizes one thing: if every child has a mother, then his own must be out there somewhere.

Having packed his little bag, put on his boots, and donned a red cape—undoubtedly a gift from his mother—Mori sets foot outside of the orphanage and begins his journey. The outside world is dangerous; ever since aliens took over Earth, humans have dwindled in numbers, and various creatures roam the vast lands and build their settlements. Ryder, a scarlet-skinned alien with horns and five eyes, encounters Mori and, realizing his origins and the dangers that await him, decides to help Mori's quest and protect him until he meets his mom.