Mermaid Swamp (人魚沼 Ningyou Numa) is a horror adventure game, made in Wolf RPG Editor by Uri, the creator of Paranoiac and the Strange Men Series. It was originally made in 2013 in Japanese; an English translation by vgperson can be found here. A remake of the game has been released in July 2018 with new CGs, puzzles, and voice acting.
Rin Yamazaki is on a trip with her college friends Yuka, Yuuta, and Seitaro. Their car breaks down in the mountains, but a kindly old man allows them to stay at his house until they can get their car fixed.
But the old man goes on a trip of his own, and during that time strange things begin happening as the characters are trapped inside. There is a legend of a mermaid who resides in the swamp outside the mansion, and it looks more and more like this mermaid is the one responsible for their predicament...
Mermaid Swamp provides examples of:
- Abduction Is Love: Deconstructed. In the legend of the mermaid, a man kidnaps a mermaid because he has fallen in love with her. This ends very poorly for the mermaid. While there is no actual mermaid, the mermaid's legend is based on events involving young women being kidnapped for precisely the same reason by the Tsuchidas, a Big, Screwed-Up Family with a fixation for girls underwater. Those incidents didn't end well either.
- And Now for Someone Completely Different: There are two instances where you end up playing as Seitaro. If Rin suffers a Heroic BSoD upon finding Yuka dead, you have to play as Seitaro to check on Yuuta. And no matter what story path you're on, when Rin goes into the mountains and gets lost, you have to play as Seitaro again.
- Big Bad: The mermaids are the ones keeping Rin and her friends trapped in the swamp house. Or so it seems, but the real villains are the spirits of the Tsuchida men, the owners of the house who imprisoned the mermaids and seek to kill the party to preserve their secret.
- Bookcase Passage: In Chie's room, there's a passage behind a bookcase where Rin finds a bunch of documents.
- Closed Circle: The protagonists' car breaks down in the mountains. They seek shelter in a nearby house, but they're stuck in the area because the power has gone out, meaning the landlines are useless and cellphones can't be charged, the fog-covered woods are nearly impossible to navigate and the old man helping them has disappeared.
- Deadly Road Trip: The four protagonists were on a road trip when their car breaks down in the cursed swamp, where they soon come to realize they're all in grave danger in some form or another. Whether the letter of the trope is played straight depends upon the actions of the player.
- Demonic Possession: Both Yuuta and Seitaro fall victim to this courtesy of the Tsuchida spirits. Yuuta acts perverted concerning Yuka and eventually becomes violent; depending on the story path, he either kills himself or chases Rin with a knife. Seitaro, meanwhile, also tries to attack Rin, either drowning her, netting you a Game Over, or chasing her with an axe.
- Don't Go Into the Woods: The nearby forest is said to be nigh-impossible to navigate without a map, and Rin is urged by Seitaro to never go there. When she inevitably does, she gets hopelessly lost, and Seitaro has to go looking for her.
- Downer Ending: The ending of the mermaid legend, where the poor mermaid suffers horribly and then dies because of someone's "love" for her. Main story-wise, three of the game's four endings are also downer endings.
- Everybody Lives: In the good ending, all four protagonists survive. In the bad endings, either everyone dies, or almost everyone dies and the lone survivor suffers Uncertain Doom or A Fate Worse Than Death.
- The paintings of Ophelia all over the house foreshadow the truth about the "mermaids". Depending on the choices the player makes throughout the game, it could also foreshadow Rin's potential fate; she has a mental breakdown from grief and drowns herself, much like Ophelia.
- The drawings and diary entries of the twins foreshadow the family's attitude towards the mermaids. Chiyo, the girl, says fish are miserable in tanks and made a drawing of a crying woman. Chie, the boy, says he loves seeing fish and draws a beautiful, happy mermaid.
- Rin's repeated dreams of being underwater and seeing someone above her foreshadows the moment when a possessed Seitaro drowns Rin in the bathtub in one of the endings.
- A Form You Are Comfortable With: It's implied that the ghost is taking on Yuka's form in order to communicate with Rin.
- Guide Dang It!: On several occasions. Followed Rin's prompting to light a fire for Yuka? Her illness kills her and the pressure of gas buildup inside her makes her explode. A possessed and crazy Yuuta kills himself under the influence and when he's bleeding out, he wonders why his neck hurts. Backed into a corner by a possessed Seitaro and forced to pick one of two options? How was the player to know that 'don't dodge' equalled 'beat the curse out of him'?
- Haunted House: The main setting of the game is in two, a main house and an old mansion, near a swamp, haunted by mermaids and the spirits of the men that lived there.
- Jerk with a Heart of Gold: Both Rin and Seitaro. Rin is obnoxious, foul-mouthed, and has a tendency to call Seitaro names. Seitaro is a know-it-all, more than a little bossy and pushy, and can name-call as well as Rin. They're also both very protective of their friends, and they both give their all to make sure everyone's okay.
- Jump Scare: There's a few. Most of them are not accompanied by a Scare Chord, which somehow makes them worse.
- Kill 'Em All: The ending "Forever Deep". Yuka dies from her illness, Yuuta stabs himself, and Seitaro and Rin commit double suicide after they find they can't escape the house.
- Multiple Endings: Three bad endings and a good one.
- Yaobikuni: Yuka, Yuuta, and Seitaro die. Rin ends up locked where the mermaids are for several days, so she ends up eating the flesh of one of the mermaids out of starvation. The old man lets her go and convinces her that she's become immortal due to eating the mermaid. The last scene shows Rin running across the forest as she laughs maniacally.
- Forever Deep: Yuka and Yuuta die. After finding the "mermaids" and trying to find a way home to no avail, Rin and Seitaro drown themselves in the swamp after realizing they can't escape.
- Secrets: Only Seitaro dies, and this sends Rin across the Despair Event Horizon. The place where the mermaids are is locked so she cannot enter. She returns to the old house and has hallucinations of Seitaro calling her from the swamp, which cause her to commit suicide by throwing herself in the swamp. A distressed Yuuta tries to save her to no avail, only to be shot to death (presumably by the old man). Only Yuka survives, and her condition has not improved.
- Underwater Dream: Everyone is saved. Rin and Seitaro enter the place the mermaids are locked and Seitaro quickly realizes they are not mermaids, just corpses of abducted women preserved in tanks. Rin blows the place up with dynamite, so the mermaids can rest in peace. The old man Tsuchida lets them go because he was not a bad guy after all, everyone is saved, and Yuka returns to normal.
- No Good Deed Goes Unpunished: You want to be nice and light a fire in Yuka's room, to warm her up? Congratulations, you just doomed her to die. Though this might have saved her from her condition killing her more slowly...
- Not Quite the Right Thing: While lighting the fireplace in Yuka's room seems like a kind thing to do since she complains about being cold, doing so ends up speeding her condition along and killing her.
- Our Mermaids Are Different: The mermaids are based upon the ones found in Japanese folklore, drawing inspiration from many different folktales and legends. According to the legend of Mermaid Swamp, mermaids really don't do well in swamp water. It's also said that eating a mermaid's flesh can make you immortal. Oh, and they can apparently come back as hideous ghosts who kidnap local girls and curse outsiders. It turns out that the 'mermaids' aren't truly mermaids, either; they're the ghosts of ordinary women were kidnapped, kept in water and treated like mermaids.
- Spiritual Successor: To Paranoiac. The house of this game even shares similar rooms, shape, and structure to the one seen in that game.
- Swamps Are Evil: The titular swamp is a cursed area where mermaids are said to haunt the waters and pull any unlucky man inside. Not helped is the two Haunted Houses nearby where the mermaids are said to reside. However, the mermaids are not the real threat — it is the Tsuchida spirts who trapped them there in the first place.