This story begins with a question about friendship between men and women—specifically, whether a “female friend” and a “male friend” can truly exist. Socially, many people debate how far such friendships can be accepted. Some argue that “they could even take a bath together” and that friendship can transcend gender, while others believe that “sharing a drink or meal alone is fine, but anything more intimate should be avoided.”

But can friendship between men and women really be maintained even in such extreme situations? To answer this question, an experiment begins in the shadows.