In this fanfiction, Lulu is likely a character who has the task of raising Naruto. She could be from a different realm or have a very different background from the Naruto universe. Maybe she's a sorceress or a wise woman with her own secrets and powers that she imparts to Naruto as he grows up.
Perhaps there is a powerful enemy that exists in both universes. Naruto and Lulu, through some magical or chakra - related means, are made aware of each other's existence. They meet and combine their unique powers. Lulu's magic and Naruto's ninjutsu could create some really cool and unexpected combat techniques, like using Lulu's polymorph spell on Naruto to give him a new form with enhanced ninja abilities.
A new villain could be created specifically for this fanfiction. This villain could be a being that feeds on the chaos between the two different universes. It has the ability to disrupt chakra flow in Naruto's world and nullify magic in Lulu's world. Naruto and Lulu would have to figure out how to work together to stop this entity before it destroys both of their homes.
In this fanfiction, it could be that there is a prophecy that involves both Lulu and Naruto. The prophecy states that only by combining their powers can they save both their universes from a great evil. So, they meet and at first have communication problems due to their different backgrounds. However, as they train together and share their stories, they form a deep bond and work towards fulfilling the prophecy.
At first, their interaction could be filled with misunderstandings. Naruto's direct and sometimes brash way of approaching things might seem strange to Lulu. However, Naruto's sense of justice would resonate with Lulu. She might see in him a kindred spirit in terms of protecting those they care about. As they interact more, Lulu could use her magic to help Naruto in situations where his ninja skills alone aren't enough, and Naruto could use his combat experience and quick thinking to get Lulu out of tight spots.
Their relationship could start with curiosity. Lulu, being the curious fae, might be interested in Veigar's dark magic. Veigar, on the other hand, might be intrigued by Lulu's ability to manipulate nature with her magic. This initial curiosity can lead to them spending more time together, gradually understanding each other.
Another option is to check out social media groups dedicated to Naruto fanfiction. Sometimes, members of these groups will post their own Naruto Lulu fanfictions or know where to find good ones. For example, on Facebook or Reddit, there are likely groups related to Naruto fanfiction that could be a great resource.
One interesting Naruto Lulu fanfiction could be about them teaming up on a special mission. Maybe they discover a new jutsu together and have to use it to defeat a powerful enemy. It could be a story full of action and adventure.
Another theme is her relationships, especially with the other characters from Final Fantasy X. For example, her relationship with Wakka is often a central point in some fanfictions, showing their bond and how they support each other.