Sex Education in 20xx
From 20xx, many people became cyborgs, saving their consciousness in the body of the machine when their bodies died to live forever. Along with that, feelings for machines were born, and emotions for AI robots. The present age is the end of the physical era and the era of living in the mechanical body. In this era, humans began to edit genes to solve growth problems, and the growth organs gradually deteriorated. As a result, sex has nothing to do with reproduction. Gender was divided into human, cyborg, and AI robots.