The story centers on a remote, isolated island called . The island has a unique and bizarre custom that is essential to its survival. Due to a curse or a special characteristic of the island's women, they are able to conceive children only on a specific day—the 7th day of a certain cycle (often interpreted as a week or a specific time of the month).
: The term can literally mean "tool girls" or might be used metaphorically. Without specific context, it's hard to discern the intended meaning. If it's related to a manga, anime, or another form of media, please provide more details for a more accurate response. koumi-jima shuu 7 de umeru mesu-tachi