Perhaps in this fanfic, the Ink Demon is a creation of Orochimaru's forbidden experiments. He was trying to create a new type of weapon but it got out of control. Naruto discovers this and decides to take it upon himself to stop the Ink Demon. He teams up with some of Orochimaru's former experiments who have turned good, like Kabuto, to find a way to reverse the Ink Demon's existence and save the world from its inky wrath.
One possible plot could be that the Ink Demon somehow gets transported to the Naruto universe. Maybe it starts causing chaos in Konoha, and Naruto has to use his new-found Sage of Six Paths powers to fight it. The Ink Demon's unique abilities, like creating ink-based creatures, would be a new and strange threat for the ninja world.
I'm not entirely sure as I haven't read that specific fanfic in detail. But generally, it might be a fan - made story that combines elements of Naruto and Bendy (the Ink Demon). It could involve Naruto characters in a situation related to the spooky and mysterious world of Bendy, perhaps with new adventures, challenges, and crossovers.
One possible plot could be that Mikoto somehow survived and she takes Naruto under her wing. She trains him secretly, using her Uchiha knowledge to make him stronger. This could lead to Naruto having a unique set of skills that no one else has.
Well, one possibility is that Naruto resigns due to feeling burnt out from all the battles and political unrest in the village. He might decide he's done his part and wants a simple life away from the chaos.
Maybe Naruto discovers some dark secrets about his family that completely shatter his world view. For example, he finds out that his father was involved in some really bad things. This revelation makes him question everything he believed in and he becomes emo as a result. He might start wearing darker clothes, cutting off his hair, and his behavior towards others becomes cold and distant.
One possible plot could be that Naruto is wrongly accused of a crime he didn't commit. Maybe he was framed by an old enemy who wants to see him suffer. While in prison, he tries to prove his innocence. He could use his ninja skills subtly to gather evidence within the prison walls, and also make some unlikely allies among the inmates who start to believe in his innocence as they get to know him better.
In a 'naruto is a uchiha fanfic', a possible plot could be that Naruto is so inspired by the Uchiha that he tries to bring back the glory of the clan. He starts by trying to understand their culture and values better. He could try to convince the village to support the revival of the Uchiha name. This would likely involve him dealing with the political aspects of the village as well as any lingering grudges against the Uchiha. He may also have to face off against those who would rather see the Uchiha stay in the past, all while learning more about the Uchiha's unique abilities and trying to incorporate them into his own fighting style.
There are probably 'naruto is evil' fanfics out there. A possible plot could be that Naruto is influenced by some dark force. This force twists his perception of right and wrong. As a result, he starts to target his former friends and allies. He might use his skills to cause chaos in the ninja world, believing that the current system is corrupt and needs to be overthrown.
It's possible that the 'demon' aspect could introduce a new power or curse to Naruto. The 'heat' might refer to a new form of chakra or energy that he has to control. And the 'lemon' could be related to a love interest. Maybe Naruto is in a relationship with a female character, and the demon influence adds a layer of complexity to their relationship, like jealousy or possessiveness due to the new power Naruto has. However, this is all speculation as we don't actually know if such a fanfiction exists.
Perhaps Naruto gets corrupted by some dark force. It changes his personality completely. He might start seeing all the people in the Hidden Leaf Village as the source of his problems. He could remember all the times he was ostracized as a child and now blames everyone for it. So in the fanfic, his hatred for everyone grows as he views the world in a new, darker light.
A plot might be that Naruto is born in the Naruto universe but has dreams and visions of Sparda. As he grows, he starts to show extraordinary powers that are not normal for a ninja. He then embarks on a journey to find out who Sparda is and discovers that he is his father. Along the way, he meets characters from the Devil May Cry universe who help him understand his powers. He has to fight against ninja clans who want to use his powers for their own gain and demons who want to corrupt him. He uses his Naruto - like tenacity and Sparda - inspired powers to overcome all these obstacles.