One common theme is the 'opposites attract' concept. Naruto is often seen as the energetic and sometimes goofy hero, while Samui is more reserved. Another theme could be 'forbidden love', as they are from different villages.
There are several common themes. Firstly, there's the theme of mutual admiration. Naruto admires Samui's strength and grace, and Samui is intrigued by Naruto's tenacity and kind heart. Secondly, the theme of cultural differences can play a big part. Since they are from different ninja villages, they have different customs and ways of life. Fanfictions might explore how they navigate these differences in their relationship. And finally, the theme of growth through love is also present. Their relationship might cause them to grow as individuals and as ninjas.
Well, a common theme is the discovery of new feelings. Naruto, who has had his heart set on other things like protecting the village and his friends, suddenly realizes he has strong feelings for Samui. Samui, on the other hand, might be initially hesitant because of their different backgrounds. Also, the theme of overcoming differences, both in their personalities and their village loyalties, is often explored in these fanfictions. They have to figure out how to be together despite the potential obstacles.