Kaikisen manga

Kaikisen summary:

The legend has it that once upon a time, a pact was sealed between the Shinto priest of the town of Amide and a mermaid. Ever since, abundant fishing has guaranteed the town’s prosperity. This pact has always been honored by the priests of the Yashiro family. However, the legend has attracted both media and property developers, and the acting priest has acceded to their demands. Yosuke, youngest of the Yashiro family, has doubts about the existence of the mermaid, but will soon change his opinion as strange occurrences begin to unfold…