Kawaki makes his appearance in Boruto manga at a specific point, but I can't recall exactly. You might want to check the official manga sources for the precise chapter.
In a 'naruto saves boruto fanfiction', Naruto might use his powerful jutsu like Rasengan to fend off enemies threatening Boruto. He could also use his experience and wisdom to guide Boruto out of a difficult situation, perhaps one involving a powerful new villain in the ninja world.
Maybe some new rogue ninja group that has a vendetta against the Uzumaki family. They see Boruto as a way to strike at Naruto, so they try to harm him, which then leads to Naruto having to save him.
One idea could be that Naruto uses his shadow clones to create a distraction while he sneaks in to save Konan. He could use his Rasengan to take out Hanzo's guards quickly.
Shikamaru might be involved. He's very intelligent and could come up with a clever plan to outmaneuver the Akatsuki. His shadow - binding jutsu could also be used to immobilize some of the Akatsuki members.
Well, one way could be that Naruto accidentally stumbles upon Itachi's plot against Mikoto. Maybe Naruto was in the right place at the right time, and using his ninja skills and his never - give - up attitude, he manages to fend off Itachi and save Mikoto. Naruto is known for his quick thinking in dangerous situations.
Well, in the fanfiction, Naruto might use his speed and agility to whisk Sasuke away from the fangirls. Maybe he creates a diversion, like using a clone to draw the fangirls' attention while he grabs Sasuke and flees to a safe place.