I'm just as confused
It's a metaphor. An umbilical cord is sometimes compared to a chain- as in, a mother having trouble letting go of an adult child might be told "It's time to cut the umbilical cord."
Lol the mom was fucking her son thats why
Which made me wonder why this was the title. So I feel like the author is trying to say with the chains shown at the end on kei that them having sex is the same as that mom n son having sex except kei is in the son's position
Ohh thanks so much
why its called umbilical sex