beta
I just noticed they are the same characters as "Strange way of love", but like in another world. Though, the art style of this mermaid looks better than the other guy of the story who I haven't read.
There's official art piece of the mermaid couple here too. And another story of the same characters, that probably not translated yet: https://www.mangago.zone/read-manga/strange_way_of_love/uu/to_chapter-1/pg-1/