These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Insane Troll Logic: Uri's games have a general trend of forcing you to choose the LEAST realistic option during a choice scene in order to get the best ending. In Mermaid Swamp, you have to NOT light the fireplace in Yuka's room, despite her constantly saying how cold she is and the game neatly handing the firewood to you. You also SHOULDN'T dodge when being attacked by Seitaro. Justified in the case of the latter, as he is under the control of the mermaids' curse.
The description of what happened to the legendary mermaid who was kept in a tank.
...and the fact that the legend was based on the Tsuchida family's fascination for keeping young women in tanks of water.
When a starving Rin gets desperate and eats the flesh of one of the "mermaids".
Squick: There are sound effects when Rin accidentally overhears Yuuta...doing things. What makes it worse was that Yuuta was thinking of Yuka. Yuka in her current swollen condition. And more disturbing still, his sudden strange fascination with Yuka mirrors that of the Tsuchida family and their reasons for sticking young women in tanks of water. And also, Yuuta was Not Himself and not acting of his own free will entirely. Yikes.