The contrast in their personalities. Naruto is often impulsive and full of energy, while Ino is more composed and calculating. In a romantic relationship, this can lead to some really interesting scenarios. They could learn from each other and grow together. For instance, Naruto could become more patient because of Ino, and Ino could become more adventurous with Naruto.
The world - building aspect. If Naruto is a king, there's a whole new world to create around him. Ino could be part of a different social class or have a special role in the kingdom. Their romance could be intertwined with the politics, the culture, and the daily life of the kingdom. It could also involve adventures outside the kingdom as they face threats together, which would make for an exciting and interesting fanfiction.
The power dynamic. Naruto as a king has a lot of power and authority, and Ino is a strong - minded character. Seeing how they interact within this power structure can be fascinating. For example, if Ino challenges Naruto's decisions in a respectful way and he respects her for it.