A possible plot is that the harem aspect involves characters from both Naruto and Familiar of Zero. Say, Hinata and Louise both develop feelings for Naruto. This could lead to a lot of jealousy and competition between them, but also moments of friendship as they realize they have more in common than they thought. Or perhaps a group of Naruto characters form a sort of alliance with the students at the Tristain Academy in Familiar of Zero, and they work together to improve relations between their two worlds, all while dealing with the harem - like relationships that develop.
One idea could be a crossover where Naruto characters end up in the world of Familiar of Zero. For example, Naruto could meet Louise and they team up to face a common enemy. Maybe an evil mage from the Familiar of Zero world is trying to steal chakra, and Naruto uses his skills to protect everyone. Another plot could be about a character from Naruto becoming a familiar in the Familiar of Zero world, which would create a lot of comical and interesting situations as they try to adapt to the new rules and customs.
One interesting plot twist could be when Naruto discovers he has a hidden power related to the Familiar of Zero world that changes his role in the story completely. Maybe he can communicate with familiars in a unique way that no one expected.
One idea could be to create a crossover where Naruto characters are transported to the world of Familiar of Zero. For example, Naruto could be mistaken for a powerful familiar. Another idea is to have a character from Familiar of Zero learn ninjutsu from Naruto. Maybe a familiar in the Familiar of Zero world could have the Nine - Tails' chakra sealed within it.
One idea could be that the protagonist from 'The Gamer' gets transported into the world of 'Familiar of Zero'. He could use his gaming skills to navigate the complex political and magical situations there. For example, he might level up in the magic system of 'Familiar of Zero' in ways that the natives find astonishing.
One idea could be a male OC who is a powerful mage from a far - off land arriving at the Tristain Academy. He could have unique magic that no one has seen before, like the ability to control time on a small scale. This would create interesting interactions with the main characters, especially Louise. Another plot could involve the male OC being a spy from a rival country, but gradually falling in love with the world of Halkeginia and having to choose between his loyalty to his homeland and his new - found friends.
Firstly, the power levels in both Naruto and Familiar of Zero are quite different. Naruto characters can be extremely powerful with their various jutsu and transformations. In Familiar of Zero, the power of mages varies greatly. Balancing these power levels in a fanfiction is a big challenge. When it comes to the harem part, it's important to develop each relationship in the harem in a unique way. You can't just have all the characters having the same kind of feelings for the main character. And then there's the cultural difference. The Japanese - inspired Naruto world and the more European - inspired Familiar of Zero world have different cultural norms that need to be considered when writing interactions between characters.
One idea could be a crossover of Naruto's world and the Familar of Zero world where Naruto has to learn the magic system in the new world. Maybe he teams up with Saito from Familar of Zero to fight a common enemy.
Perhaps in the fanfiction, the Zero Tails is a manifestation of the negative emotions of the ninja world as a whole. A group of young ninjas discover this and they try to find a way to purify the Zero Tails. They seek the help of old sages and learn ancient jutsu to attempt this purification, which could lead to a battle against those who want to keep the Zero Tails as a weapon of mass destruction.
One idea could be exploring new ninja techniques not seen in the original Naruto series. For example, a unique combination of elemental jutsus created by a character in 'naruto ruler zero fanfiction'.
The new characters, for one. When original characters are well - crafted, they can add fresh dynamics to the existing Familiar of Zero world. Also, the harem aspect can bring in different relationship dynamics and romances that can be exciting to read about.
One interesting idea could be the interaction between the different power systems of 'Overlord' and 'Familiar of Zero'. For example, how the magic in 'Familiar of Zero' might interact with the various abilities of the characters in 'Overlord'.