Lenia, the youngest daughter of the Sea Queen, has always been fascinated by humans and the dry world. When Christopher, prince of the Southern Kingdom, almost drowns in a shipwreck, Lenia impulsively rescues him and brings him to a beach near a convent. One of the women there is Margrethe, princess of the Northern Kingdom, who is living in hiding as a nun to protect her from Southern invaders. Christopher's rescue changes the lives of both Lenia and Margrethe.
Mermaid contains examples of:
- Altar Diplomacy: The Northern and Southern Kingdoms used to be one country that split in two before Margrethe was born. The two kingdoms have been fighting on and off ever since. Margrethe hopes that by marrying Christopher, she can unite the two and stop the fighting.
- Cheerful Funeral: When a merperson turns into foam and becomes part of the sea, others celebrate their passing with song and feast. Lenia is one of the few who feel that death is a terrible loss, rather than something to be accepted and celebrated.
- Dead Guy Junior: Christopher names his and Lenia's daughter Christina, after his late grandmother.
- Empty Bedroom Grieving: After Margrethe's mother died two years ago, the king banned anyone from entering her chambers except the maids who keep the rooms maintained just as they were when she was alive.
- Foul First Drink: While exploring a shipwreck, Lenia finds a jug tipped over on the floor, with rum still inside it. She takes a sip, immediately spits it out, and eats some fish and sea flowers to get rid of the awful taste.
- The Grand Hunt: Christopher takes the transformed Lenia along on a hunting expedition. She loves riding her horse because it reminds her of swimming through the ocean, but she's horrified by the violence of the kill. The stag seems nearly human, unlike the fish and sea plants Lenia used to eat.
- Heaven Seeker: Most merfolk consider themselves better off than humans because they live for 300 years, and because they gracefully dissolve into foam when they die instead of rotting. But Lenia hates the thought of her mind and memories disappearing when she dies. She wants to live forever in Heaven, like humans do.
- Lighting Bug: The Sea Queen lights her palace with bioluminescent fish.
- Long Last Look: After the sea witch gives Lenia the potion that will make her a human, she swims slowly through her parents' palace, peering in on her sleeping family and trying to memorize every detail, before she finally sets off on the journey to the shore near Christopher's palace.
- Masquerade: Once mermaids regularly visited the surface, but as humans started traveling more by sea, this became increasingly dangerous. After a group of mermaid sisters were killed by fishermen, Lenia's great-grandmother banned interaction between mermaids and humans. Now merfolk are allowed to visit the surface only once, on their eighteenth birthdays, and they must stay out of sight of humans.
- My Eyes Are Leaking: Lenia is shocked when Margrethe's eyes fill with water.
- Painful Transformation: Lenia passes out from the pain of her tail ripping in half and her scales dissolving.
- Power at a Price: The sea witch can only create magic by mixing her blood with the most valuable thing someone has, like Lenia's voice or her sisters' hair.
- Private Tutor: Gregor was Margrethe's tutor when she was a child, as well as her father's. He's still one of the people she trusts most, and he helps her carry out her plan to run away to the Southern Kingdom to marry Christopher.
- Protection from the Elements: The mermaids' thick, hard, opalescent skin protects them from the cold, so they can swim naked during winter and still be comfortable.
- Rescue Romance: Lenia saves Christopher from the shipwreck and carries him to shore. Margrethe sees the two of them, wraps Christopher in her furs, and runs back to the convent to summon help. Both Lenia and Margrethe fall in love with him.
- Sent Into Hiding: Margrethe and her lady-in-waiting Edele are both living in disguise as novice nuns due to increased tensions with the Southern Kingdom. Margrethe is bored and lonely, and Edele even more so, even though they're both given more freedom than the actual nuns.
- Signature Scent:
- Margrethe remembers her mother as smelling like lavender.
- Christopher's sister Katrina smells pleasantly of flowers.
- The Soulless: Merfolk have no souls. When they turn into foam, they disappear forever. Lenia's grandmother has told her that souls are webs of light that contain the essence of who a person was and live on forever after the body dies, and Lenia desperately wants one.
- Switching P.O.V.: Lenia and Margrethe take turns narrating each chapter.
- Tongue Trauma: To make the potion that will turn Lenia into a human, the sea witch cuts her tongue out and drops it in the cauldron.
