Lambo could also be part of the story. His antics in the past could either cause trouble for Tsuna or, in a comical way, help Tsuna achieve his goals. For instance, his love for food might lead them to discover a hidden place or a secret item that turns out to be important in the grand scheme of things.
Hayato Gokudera would be a key character. In the time - travel scenario, he might be initially confused by Tsuna's changed behavior (due to his future knowledge). But then he would quickly side with Tsuna and help him in whatever plans he has. He could also learn from Tsuna's future self and become an even more powerful right - hand man.
Reborn is often involved. Since he is Tsuna's mentor, he could play a crucial role in guiding Tsuna during his time - traveling adventures. Maybe he has some knowledge about time travel that he imparts to Tsuna.
Another plot could be Tsuna traveling back to a time when his father was still around. He could get to know his father better and learn some hidden family secrets. This would not only strengthen their relationship but also give Tsuna an edge in his future as the Vongola boss. He might learn about some special powers or techniques that his father knew but never got to pass on to him in the original timeline.
Obviously, Josuke himself would be the main character. His friends like Okuyasu could also be involved. Maybe Okuyasu somehow follows Josuke back in time or Josuke has to find a way to bring him back if he gets left behind in the past.
Obviously, Aria herself is the main character. Her family members like her mother and father could be important characters, offering support or having different opinions. Her best friends would also be likely to be involved, providing emotional support or getting into some friendly arguments about how she should handle the pregnancy.
In addition to the main characters, there could be some minor characters from the manga. For instance, the teachers at UA like Aizawa. Aizawa might notice that something is different about Deku and start to investigate. There could also be villains from the past that Deku has to face again, but this time with his future knowledge. Characters like Stain could be interesting to include as Deku might try to change the way he dealt with Stain in the original timeline.
Obviously, Kushina herself would be a central character. Minato could also be involved, perhaps in a complex relationship triangle with Naruto and Kushina. Then there are other female ninjas like Tsunade. She might be intrigued by Naruto's time - traveling knowledge and get involved in the story. Sakura could also be a potential character. If she somehow gets dragged into the time travel, she might have her own role in the harem - like situation around Naruto.
Hermione Granger could be one. Her intelligence and thirst for knowledge might make her interested in a time - traveling character. Ginny Weasley is also a likely candidate. She's brave and has her own charm. And Luna Lovegood, with her unique view of the world, would probably be drawn to the mystery of time travel. Another potential character could be Pansy Parkinson. Her strong - willed nature might lead her to be part of the harem in a different way compared to the others.
Well, there could be her best friend who is always there for her during the pregnancy, giving her advice and emotional support. There might also be a mysterious figure, like an old wise woman who has knowledge about pregnancies in special circumstances that Tera Faya's case might be. And of course, there could be a rival of some sort, who might try to use her pregnancy against her in some way.
Igneel could also play a role. Since Igneel was Natsu's adoptive dragon father, he could appear in Natsu's mind during the transformation, guiding him and giving him advice on how to handle his new dragon powers. And there could be other dragons in the story as well. They might be either friendly or hostile towards Natsu depending on their nature.
There could also be new characters introduced. Maybe other magizoologists from different parts of the wizarding world. They could have different approaches and beliefs about magical creatures. Some might be rivals, trying to outdo Harry in the discovery and study of new species, while others could be mentors, guiding him in the complex world of magizoology.