Chapter 12 is built around a strong anti-individualism. Nothing in creation exists for itself alone. Human beings, their bodies, and even their capacity for love are oriented toward the partner, which means the self is completed only through rightly ordered relationship.
The chapter applies this most directly to sexual ethics. Conjugal love is holy because love is received from the other rather than possessed by the isolated self, so false ownership and self-directed use of sexuality become central symptoms of the Fall.
It also portrays true love as absolute and unchanging rather than evolutionary or experimental. In that logic, free sex and radical self-ownership share a root because both deny that love is covenantal, relational, and ordered toward the other.