The theme of this manga is the conflict between hiding your true self versus sharing the undesirable aspects of yourself despite the risk of people rejecting you. Poppy's undesirable "true self" is the fact that he's an android. Takashi's is the fact that he's an earthling, and consequently has to crudely jam food into his facial mouth rather than his abdominal mouth. The most important scene is when Poppy cries at Takashi's suggestion that he keep his robot-ness a secret. Hiding aspects of himself would be the antithesis of self-love, of self-respect, and would be tantamount to saying that there was something wrong with himself. And even though this is just a oneshot and we don't see whether the two of them are actually able to make friends or not, at least we're left knowing that Poppy (and presumably Takashi) will live their lives with self-respect and integrity and will continue to persevere despite the constant rejection. Though if this manga was more than a oneshot, portraying that perseverence would make this a much less optimistic manga as it would have to show the slow chipping away at their self-esteem.