One idea could be that an unknown entity with angelic powers emerges in the Naruto world during a time of great turmoil. This entity could initially be seen as a threat but later turns out to be a force for good, helping Naruto and his friends in unexpected ways. For example, it might use its 'angel of darkness' powers to purify the corrupted chakra in some of the villains, turning them into allies.
One idea could be exploring the origin of the 'crimson darkness'. Maybe it was created by an ancient and powerful magic that has been lost over time. Another could be a story about a hero who has to face the crimson darkness alone and discovers a way to purify it.
One idea could be a crossover where Naruto characters end up in the afterlife world of Angel Beats. For example, Naruto and his friends could try to help the SSS members achieve their unfulfilled wishes. Another idea is to have a character from Angel Beats gain ninja powers like in Naruto. They could then use these powers to fight against the Angel in a new and unexpected way. A third idea might be a story where the concept of chakra exists in the Angel Beats world, and the characters have to learn how to control it.
A plot could involve Angel protecting Willow from a group of vampire hunters who mistake her for a dark witch. Along the way, they develop a deeper understanding of each other and their respective roles in the fight against evil. They might also discover a long - lost prophecy that involves both of them and has to do with saving the world.
A plot could revolve around a group of heroes who use angel blades to fight against a new, powerful dark force. They have to discover the true potential of the angel blades and how to combine their powers to defeat the enemy. For example, they might find that when all the blades are united, they can open a portal to a dimension where the dark force originated, allowing them to face it on its home ground.
A great plot idea could be that the shotgun the angel has is actually a cursed weapon. The angel has to figure out how to break the curse without losing the weapon's power. Or perhaps the fanfic could center around the angel's relationship with other celestial beings. They might not approve of the angel's violent methods with the shotgun and try to stop the angel from using it. This could lead to a conflict within the celestial realm.
Maybe a plot where the darkness bloodline holder has to hide their power in the early stages due to the stigma associated with it in the Naruto world. As they progress, they gradually learn to control and use it for good, facing many challenges along the way, like dealing with those who want to use their power for evil. They might also encounter ancient secrets related to the bloodline that could change the entire Naruto universe's power balance.
One idea could be exploring the darker sides of the ninja villages that are usually hidden. For example, the corruption within the political systems of the villages. Another could be focusing on characters who have turned to the dark side due to past traumas, like a character who lost their family in a war and then joined a dark organization. Maybe also a plot where the traditional ninja values are being twisted in the 'world of darkness' version, leading to moral dilemmas for the main characters.
Well, you could write a fanfic where the God of Darkness decides to test the main RWBY characters. He creates a series of trials that are designed to push their limits, both physically and mentally. This would allow for a lot of character development as they struggle to overcome these challenges. It could also show how they interact with the power and presence of the God of Darkness.
One idea could be that an angel and a devil are forced to work together to save the world from a greater evil. They start off hating each other but gradually learn to respect and even care for one another.
One idea could be exploring the backstory of a minor character in 'into darkness'. For example, a crew member who has a hidden past related to the main antagonist. Another could be a time - travel plot where a character goes back in time to prevent the events that led to the 'darkness' in the story. Maybe also a story about a character who discovers a new power or ability that could change the course of the events in the 'into darkness' universe.