In this fanfiction, a great concept might be the cultural exchange. The Breath of the Sun might come from a different cultural background than the Naruto universe. So, seeing how the two cultures interact and influence each other could be fascinating. For instance, the values and traditions associated with the Breath of the Sun could impact how Naruto and his friends view things like honor and loyalty. And perhaps there are new story arcs that revolve around protecting the secrets of the Breath of the Sun from those who would misuse it.
One interesting concept could be the fusion of Naruto's ninja abilities with the unique powers from 'Breath of the Sun'. For example, Naruto might use his chakra in new ways inspired by the Breath of the Sun techniques. Another concept could be the new characters or clans that are introduced in this fanfiction. They might have abilities related to both Naruto's world and the Breath of the Sun concept. Also, the story could explore how the ninja world would react to the sudden appearance of these new powers and how they would be integrated into the existing power structure.