We all saw this ending coming, but nowadays that's the case for any kind of romance manga. If you can't see the ending coming from miles away, it's "poor writing" and "too sudden of a change in the plot point in an attempt to be original" so there's not really any good way to end a romance manga anyways.
Nevertheless, I enjoyed reading this, even if it was mediocre and predictable. I guess it's all in the way it's presented