So I've seen the whole 'Math's Saddest Love Stories' (asymptotes that drift ever closer but never meet etc.), but I think we're missing the potential of Math's Funny Love Stories.
The couple whose destiny is an infinite cycle of breaking up and getting back together again:
Oscillating rapidly in and out of each other's life for a while before drifting apart in opposite directions:
Drifting ever closer, until you finally meet and go fuck that:
One who drifts slowly closer to the other, until they acutally meet and decide to make a very sharp turn in the other direction:
Whatever hellscape of contrived coincidences these series of infinite near misses are:
Who needs a new fanfic challenge?