I'm not sure if there is such a specific fanfic available online. Fanfics can be quite diverse and hard to track down, especially with such a specific and rather unusual title. It might be a very niche creation within a particular fan community.
Power - building is a common theme. The OC usually starts off with some sort of special ability or knowledge and uses it to gain more power in the Highschool DxD universe. This power - building often attracts the attention of various female characters, leading to the formation of the harem.
One popular 'godlike naruto massive harem fanfiction' is 'Naruto: The Harem King'. It has an interesting plot where Naruto is given god - like powers and attracts a large number of female characters. The story also has some exciting battles and character developments.
There's also 'Rising of the OC in DxD'. In this fanfiction, the OC is a reincarnated being. He uses his past - life knowledge to his advantage in the world of Highschool DxD. His harem includes characters from different factions, and the story delves into how he manages to keep them all together while facing various challenges from the supernatural world.
In 'naruto massive chakra fanfiction', a really cool concept could be the combination of different chakra natures in ways that are not seen in the original series. For instance, combining fire and water chakra to create a new type of energy that has both the offensive power of fire and the adaptability of water. This can lead to really unique battle scenarios and character abilities.
Often, characters with huge amounts of chakra are considered powerful. Naruto himself might be even more powerful in fanfiction, with his already massive chakra reaching new heights. Sasuke could also be a top - tier character, his Sharingan combined with a large chakra reserve making him a force to be reckoned with.
You can start by looking on fanfiction platforms like FanFiction.net or Archive of Our Own. These sites have a large collection of Naruto fanfictions involving Kaguya. Just use their search functions and type in relevant keywords like 'Naruto Kaguya' to find some great reads.
Well - developed characters. If the fanfiction delves deeper into Kaguya's character, perhaps showing her more human side or her motives in a more complex way. And for Naruto, it could show his growth in a new and interesting light, like how he adapts to dealing with Kaguya in a non - combat scenario. Also, good character interactions between them, such as intelligent conversations that reveal more about their personalities.
A cool concept could also be the cultural exchange. If Naruto's world collides with a world like Avatar: The Last Airbender, there would be a mix of different cultures. The ninja culture with the four - nation culture of Avatar. This could result in new ways of training, new forms of bending techniques influenced by ninja arts, and new relationships between characters from both universes.
One common theme is the development of relationships. Since it's a harem concept, it focuses on how Naruto forms bonds with multiple female characters. Another theme is often Naruto's growth. He has to adapt to having so many people interested in him, which can lead to his personal and ninja - like growth.