One common theme is the discovery of hidden feelings. Usually, Naruto and Sakura have been friends for a long time, but in these fanfictions, they start to realize there's more to their relationship. Another theme is the power of friendship evolving into love. Their long - standing bond as comrades slowly transforms into a romantic one.
Adventure is also a frequent theme. They often go on missions together, and during these adventures, their relationship deepens. For example, they might face a powerful enemy that forces them to rely on each other even more, which in turn makes their feelings for each other stronger. And of course, the theme of redemption sometimes plays a role. Maybe Naruto or Sakura has made a mistake in the past, and through their relationship, they find a way to make up for it.