There are rumors among humans that mermaids have an unparalleled appearance. The scales on their bodies can cure all diseases and can even lead to immortality. But how many humans have ever seen a mermaid alive?
The mermaid tribe has always used concentric knots to tie up those who are obedient and helpful to them for life. With concentric knots, people cannot leave the mermaids at will and have feelings for other people at will, otherwise unexpected consequences are waiting for them.
The concentric knot ties the hearts of two people that cannot be separated. If a person ties a knot with a fish, what is tied is the heart, but what is moved is the emotion! People and fish sympathize with each other, so where should they go...
Concept: Love across species