In a traditionalist society, a random hookup means we are now husband and wife

That’s the basic idea here, a modern society that is still traditional in some ways.  To these people simply having sex once makes a couple married (presumably harsh consequences for when it happens when one or both are already married.  Or maybe there is polygamy here, we can figure that out in setup).

Even with this been the case, lust/hormones/love often lead to early marriage, it is rather common (though far from universal) for people to end up married as teens, sometimes even to a stranger or near stranger.  That said, no one questions the system or even considers it might be another way.  It is simply a natural fact that sex=marriage.  We could consider something else to justify or make it harder for people to try to lie about it too.

Lot of sex but exploring how such a relationship would develop and how such a society would work.  I’d consider playing either the man or woman, they could could be teens or could be older.