Both stories start with human girl without will to live. Girls meet non-human creatures, who they start developing relationships with. Even though both stories have romance in them, Niehime to Kemono no Ou as a shoujo is more focused on it.
- Mutual exploration of feelings and purpose
- Being unable to recognize one's own strengths
- Drawing comfort from the company of another
Both main female leads have no intention of living long, and instead commit to the idea of being "useful". Instead, a non-human figure with authority deviates them from their path of sacrifice.
These male characters are drawn to their respective female's strive for new purpose. Both female leads are unable to see their value and believe their new objectives starts with becoming less of a hindrance to the one they care for.
- Supernatural (though switched where Esther is magical in Kuro vs Leo in Niehime)
- Protagonist (Salphie + Esther) wants to save/help her partner
- Both seem cinderella-esque where they're coming from a poor background being saved by a richer person (In Niehime it is the king, in Kuro he's an earl)
Both are set in a fantasy world. "Niehime to Kemono no Ou" is about its own world, where a young lady gets sacrificed to the demon king but becomes attached to him. "Koushaku Reijou no Tashinami" is about a girl getting reborn into an Otome Game as the villianess and avoids her fate and uses her old world knowledge to better the land her father hands to her.
Both of these have demons, monsters and humans in them. However, "Niehime to Kemono no Ou" is about its own world while "Yasei no Last Boss ga Arawareta!: Kokuyoku no Haou" is about being stuck in a game world.