Just learned about this manga, it's a fascinating horror. No actually yuri so far tho.
The mermaid, while misunderstood, is also very clearly not following human logic. Now appears to be turning girls into mermaids. I imagine this will lead to the town turning against her again like in the legend.
The town itself has a very strange vibe -- while at the same time they hate anyone who leaves the town and want students to "give up" to the sleepiness of the town, they also dislike anyone resembling or conversing with the mermaid, even though the mermaid is exactly what seems to cause this sleepiness.
Also, the water is clearly contaminated with mermaid juice, right?