It is not a concrete god, with no temples and believers; it is not an ancient curse, with no incantation to break. It is the cold logic in the underlying code of the universe, an irreversible law in the operation of the world, and a death sentence that has been engraved into the soul when love was born.
Under this set of rules, "falling in love" is allowed, even encouraged—just like a flower is allowed to bloom. But "together" is absolutely prohibited. Any form of "staying together" will trigger the automatic correction mechanism of the rules.
How do the rules work? It never interferes harshly. Like the most brilliant playwright, it uses the most natural way to break apart every pair of deeply loved souls:
Memory erasure method - when you are deeply in love, the memory of one or both parties will be precisely erased. It's not amnesia, but "reconstruction": you still remember each other, but those moments that define "love" - the touching that your heart beats faster, the whispers you confide in late at night, the look in your eyes that decides to spend a lifetime together - will be quietly taken away from the timeline. You have become "the most familiar stranger", remembering everything you have experienced together, except why you love each other.
Fate Intervention - When the memory cannot be erased, the rules will activate physical isolation. A sudden cross-country transfer, a family migration without warning, or even a wrong ticket or a wrong turn. You will keep missing each other, like two magnets set to the same pole. The closer you get, the faster they will separate.