One common theme is the development of relationships. Since it's a harem, Naruto has to build different kinds of relationships with multiple characters. Another theme is the use of jutsu in a creative way to attract or interact with the harem members.
One interesting concept could be how the harem aspect affects Naruto's relationships with different characters. For example, it might show new dynamics between him and his female comrades as they all vie for his attention in a different way than in the original story.
I'm not sure specifically as I haven't read this particular fanfic. But generally, in a Naruto fanfic with a harem jutsu theme, it might involve Naruto using his harem jutsu in new and unexpected ways, perhaps in some sort of adventure where his unique jutsu plays a key role in interactions with other characters.
One popular 'naruto harem jutsu fanfic' is 'Naruto: The Harem King'. It has an interesting plot where Naruto uses his charm and unique jutsu to attract a group of female characters. Another one could be 'Naruto's Harem Adventure' which focuses on Naruto's journey with a harem of characters in different scenarios.
Obviously Naruto is one of the main characters. And then there are usually some of the female characters from the Naruto series like Sakura, Hinata, and maybe even some of the female ninja from other villages. They are often part of the harem that revolves around Naruto.
The combination of two very different universes, Naruto and DxD, makes it interesting. The Reverse Harem Jutsu from Naruto is a fun element to introduce into the DxD world. It can lead to some really unique and unexpected interactions between the characters from both series.
Since 'lemon' implies adult - related content, which is not something that is widely promoted or considered appropriate in the Naruto fanfic community. For regular Naruto x harem jutsu fanfics, popularity can vary. Some might be popular because they explore Naruto's character development in a new light, like showing how he matures in handling relationships with his peers while using the harem jutsu in creative ways during battles or missions.
In fanfiction, the Naruto Reverse Harem Jutsu used on Kaguya could lead to some really interesting scenarios. Maybe it could be used as a comical moment to catch Kaguya off - guard. For example, she might be in the middle of some grand, menacing plan when suddenly the jutsu is cast and she's surrounded by a bunch of Naruto clones all vying for her attention in a rather silly way. This could potentially disrupt her concentration and give the protagonists an advantage in the fight.
Well, finding such a specific 'Naruto Reverse Harem Jutsu DxD Fanfic' can be a bit tricky. One way is to join Naruto or DxD related fan groups on social media platforms. There, you can ask fellow fans if they know of any good fanfics that combine these two elements. They might be able to point you to some hidden gems that you wouldn't find through a normal search.
One idea could be a fanfic where a young ninja discovers a unique way to combine lightning jutsu with other elements like water, creating a new and powerful technique. This could lead to him being sought after by different clans for his knowledge.