I'm not sure specifically as I haven't read it. It could be about various things. Maybe it has a science - fiction theme related to ultraviolet light, like some sort of adventure in a world where ultraviolet phenomena play a major role.
Well, without having read this particular 'naruto descendant of ultraviolet fanfic', it's hard to say precisely. It could be that the author has created a new character who is a descendant in the Naruto world and this character has some unique abilities or a backstory related to ultraviolet. Maybe it's a story about how this descendant uses their special connection to ultraviolet to face challenges in the ninja world, like fighting against powerful enemies or uncovering hidden secrets.
The setting can be a crucial element as well. Some fanfics place them in a post - apocalyptic Central City, which changes the dynamics of their relationship and the challenges they face. Others might keep it in the more traditional Flash - verse but introduce new elements specific to Ultraviolet.