Haru and Natsu are not human. They have no concept of being anything other than robots. After being abandoned by their former owner, Haru and Natsu are taken in by a scientist named Masa. Haru desires to feel, to understand how to behave like a human, and to comprehend the meaning of love. Natsu, however, is simply terrified of being abandoned once more. While Haru strives for positivity, his companion is left to sink into his own negative thoughts. Again and again, they pose the same question: what is love?