One possible plot could be that Naruto discovers he has some hidden Otsutsuki bloodline. This leads to him being ostracized by some in the village who fear his new - found power. He then has to go on a journey to learn about his Otsutsuki heritage, facing challenges along the way and also having to prove that he's still the same Naruto at heart.
One possible plot could be that Naruto discovers he has Otsutsuki blood in him. This could lead to him having new and uncontrollable powers that he has to learn to master. He might be shunned by some in Konoha who fear his newfound abilities, while others see it as an opportunity for Konoha to become even stronger. Naruto would then have to struggle with his identity and prove that he is still the same Naruto they know and love.
The plot could involve Kaguya's influence on the OC. Maybe the OC is a new being in the Naruto universe and Kaguya sees potential in them. For example, she could want to use the OC to regain her full power or to create chaos in the shinobi world again. The OC might initially be in awe of Kaguya but then realize her true intentions and have to fight against her.
In this fanfiction, perhaps Ashura Otsutsuki in the mindscape is trying to convey a message about an upcoming threat to the Naruto world. He could be guiding the protagonist to gather certain artifacts or allies to face this threat. For example, he might lead the character to an ancient temple where a powerful weapon lies, which is crucial to defeat the new enemy.
Another plot twist could be that Kaguya kidnaps Naruto to use his connection to the Nine - Tails. She might be trying to gain control over the Nine - Tails' power for herself. But Naruto, being the resilient character he is, manages to resist her control and instead starts to influence Kaguya. He might make her see the error of her ways or at least make her question her motives.
One interesting concept could be exploring the unique powers of the Otsutsuki clan in more depth. For example, how their different doujutsu abilities interact with the existing ninja world. Another could be delving into the backstories of Otsutsuki characters that were not fully explored in the original Naruto series.
One great 'Naruto Kaguya Otsutsuki Fanfic' is 'The Legacy of Kaguya'. It explores her backstory in a very detailed way. It shows how she came to be the powerful being she was in the Naruto series. The author does a great job of creating new scenarios that fit well with the existing Naruto lore.
Some characters might be in awe of him. For example, his friends like Sakura and Kakashi could see him in a new light. They might be more cautious around him at first, not fully understanding the implications of his new bloodline. His enemies, on the other hand, would likely be more fearful or more determined to defeat him. The Hidden Leaf Village might also have a different attitude towards him. They could be both proud that one of their own has such a powerful bloodline, but also worried about the potential danger it could bring.
Yes, it could be. The Otsutsuki clan has a significant presence in the Naruto series. Their unique powers and mysterious origin make them quite interesting. A fanfic exploring Naruto's relation to them in a new way might attract fans who are eager to see different interpretations of the story and characters.
The combination of two very different universes. Naruto's ninja world with its jutsus and shinobi culture, and DxD's world of devils, angels and supernatural beings. It creates a whole new set of possibilities for stories.
A unique plot makes a 'Naruto Kaguya Otsutsuki Fanfic' stand out. For example, if it gives a new perspective on Kaguya's motives. Maybe she had reasons for her actions that were not fully explored in the original series.