The “them and us” aspect of Lilly Prospero And The Mermaid’s Curse is present throughout.
When Lilly and Saffron first meet the mermaids, Lilly responds with fear as they look different and she has not seen anyone who looks like that before. Equally so, the mermaids respond with serious distrust for the humans due to the oppression the humans have put them under.
The debate rages through the story, whether a different race deserves different respect or consideration.
The humans argument, from the Harvester and Opal’s coven, is that humans are a superior species and to ensure their survival and health it is acceptable to sacrifice certain “other beings.” Juxtaposed against this is the Ancient’s view that as the humans have attacked the Mer and are willing to kill them, they are justified in wiping them out.
Both views are extreme, and result in death to lives purely based on the fact they are “different”. This is something we see in the world constantly. If people look different or live differently, they are classed as “Other” and not as worthy of respect and protection, whereas both humans and Mer, and other Beings, are all entitled to lives without attack from anyone else.
Feeling alone in the world crops up repeatedly.
Saffron feels alone as she is the only person born mortal and now with power, and the only person who has died and is now alive by the grace of another person’s existence.
Coral feels alone as both her parents are dead and she is being raised by a grandmother who, whilst devoted to her in many ways, is emotionally absent in many ways too. She is talented and strong with her magic but feels nobody is around her to appreciate her full potential.
Sam feels alone as he is raised by a father who sees him purely as a project, and a disappointing one at that. Raised in a world entirely built around magic and what can be achieved with magic, Sam is without power and unable to be a real part of the world he’s in. He’s not fully committed to the Harvesting he’s being trained in, but too emotionally isolated to know how to escape it.
This isolation ends in tragedy for Coral and Sam. Sam ends up killing Coral out of loyalty to his father, who also ends up dead. Coral ends up sacrificing herself to be part of something and to feel connected at last.
The only one who comes through it is Saffron who tries to escape her lonliness by giving her life to the Mer, but realises she is not as alone as she had previously felt because she has the love and respect of Lilly.