For the Danny Phantom side, Sam Manson could be a main character in the fanfiction. Her strong - willed and goth - like personality could contrast well with the Sekirei characters. In the Sekirei world, Kazehana could be a main character. She is a seductive and powerful Sekirei. The interaction between Sam and Kazehana could be really interesting, with Sam trying to resist Kazehana's charm while also having to work with her to solve a common problem, and Danny would be in the middle trying to keep the peace between them.
Danny would be one of the main characters, no doubt. And from the Sekirei series, Musubi could be a key character in the fanfiction. She is one of the more prominent Sekirei, being kind - hearted and strong. Her naivete might lead to some humorous situations when she first meets Danny. Also, Tucker Foley from Danny Phantom could be another main character. He could use his tech - savvy skills to help in the Sekirei world, perhaps by creating some new gadgets that work in that universe as well.
A really cool plot could be that there is a threat to both the Danny Phantom universe and the Sekirei universe. Some sort of dark entity that can traverse between the two worlds. Danny and a group of Sekirei have to team up to stop this entity. The Sekirei can use their combat skills and unique powers, while Danny uses his ghost powers. Along the way, they learn from each other, with Danny teaching the Sekirei about the concept of ghosts and the Sekirei showing Danny different ways of fighting that he hadn't seen before.
There could also be other ghosts from the Danny Phantom universe that make an appearance in the fanfiction. For example, Ember could show up and cause some trouble. She might try to manipulate Skulker or Danny for her own purposes, like getting more attention from the living or causing chaos in the Ghost Zone. This would add more complexity to the story and the relationship between Danny and Skulker.
Well, clearly Danny Phantom and Kitty are the main characters. Danny is a half - ghost boy with the ability to transform and use various ghost powers. Kitty is a sassy and strong ghost girl with her own set of powers and a distinct personality.
Danny's parents could be main characters too. They might be trying to throw Danny a normal human birthday party, completely unaware of the ghostly happenings that often surround their son. Their attempts to have a 'normal' celebration could be constantly interrupted by Danny having to slip away to deal with ghost problems. This would create an interesting dynamic between Danny trying to keep his double life a secret from his parents while still enjoying his birthday with them.
Perhaps a rogue ghost who has managed to hack into Cybertronian technology. This ghost, let's call it Techno - Ghoul, has the ability to possess and control Transformers. He starts causing chaos by making Autobots and Decepticons fight each other. Danny Phantom has to use his ghost - hunting skills and his knowledge of both the human and ghost worlds to find a way to exorcise Techno - Ghoul from the Cybertronian systems.
A powerful ghost who has found a way to corrupt Pandora's magic could be the main antagonist. This ghost might want to use Pandora's magic to gain more power in the ghost zone and the human world. It could start by causing chaos on Pandora, and then Danny would have to step in to stop it.
Tucker Foley and Sam Manson are also often main characters. They are Danny's best friends in both his human and ghost - fighting life, so they play important roles in many fanfictions. They might be helping Danny deal with the challenges of his dual identity or getting involved in his battles against ghosts.
Well, clearly Danny Phantom is a key character. He's constantly in the middle of things, trying to keep the balance between the human world and the Ghost Zone. Ember, on the other hand, with her fiery red hair and her musical powers, is another main character. In this fanfiction, their interactions are what drive the story forward, whether it's them fighting against each other at first or eventually working together.
Obviously, the main character would be Danny Phantom himself, but in two different forms or versions. One would be the original Danny Phantom from the canon source, and the other would be a version created by the fanfiction. There might also be his friends like Sam and Tucker who could play important roles in helping the two Dannys understand each other and deal with any issues that arise from their meeting.
Besides Danny, the main characters could include some of the friendly ghosts from the Ghost Zone. They could be like Danny's support system in this new motherhood journey. Also, the school bully Dash might be in the story. He could start off making fun of Danny but then gradually come to understand and respect Danny's new role. And there could be a mysterious ghostly figure that either helps or hinders Danny in his newfound motherly duties.