Well, one possibility could be that Naruto uses his ninja skills to protect Mikoto and Hitomi from some common enemy in the Naruto universe, like rogue ninjas. Maybe they are on a mission together and Naruto's strength and quick thinking come in handy to keep them safe.
In this fanfiction, perhaps Naruto helps Mikoto and Hitomi in a more personal way. For example, Mikoto and Hitomi are having trouble with some family or village - related issues. Naruto, with his own experiences of being an outcast and then finding his place, can offer them advice and support. He could use his influence in the village to help them solve their problems.
It could be that there is a special event or competition in the village. Mikoto and Hitomi are participants but face some difficulties. Naruto, being the hero he is, steps in to help them train. He shares his unique techniques and training methods. Along the way, they also become good friends and learn a lot from each other, which in turn helps them perform better in the event.