A wise old hermit could be a main character. The hermit, living in seclusion, has knowledge about the dragons that no one else does. When the last dragon comes to him for help, he uses his wisdom and his connection to nature to guide the dragon on a journey to restore its species, all while facing various challenges along the way.
The main character is most likely the last dragon itself. But there could also be other important characters like a brave knight who tries to befriend the dragon, or a wizard who has some connection to the dragon's past.
The obvious main characters would be the donkey and the dragon.
A brave knight could be a main character. They might be on a quest to find the dragon knot to save their kingdom from a dragon threat, believing that the knot holds the key to controlling the dragons.
Maybe a new Saiyan who was born on a different planet and has a different understanding of Saiyan culture. He or she could come to Earth and interact with the existing Dragon Ball characters, bringing new fighting styles and a fresh perspective to the story.
The main characters could be a young adventurer who stumbles upon the blue dragon and the delphinium. Or perhaps a wizard who has been studying the delphinium's magical properties and then has an encounter with the blue dragon.
In 'Raya and the Last Dragon novel', Raya is the central figure. She is a brave and determined girl. The last dragon is a significant character as well. It is a mysterious and powerful being. There could be other characters such as Raya's family members who might have influenced her decision to start the journey in the first place, and also the people she meets in different regions of her world. These could include people from different tribes or communities that have their own cultures and ways of life, which all play a part in the overall story.
Obviously Naruto would be one of the main characters. There might also be his friends like Sasuke, Sakura, and Kakashi. The dragon itself could also be considered a main character in a way, as the whole story seems to revolve around it.
Raya is an obvious choice. Her journey to reunite Kumandra and her strong will make her a great focal point.
It could be Harry Potter himself as he often has to face powerful and symbolic foes. He might be the one to interact with the dragon, the lion and the serpent in some way.
I don't know for sure, but I would guess there are the children, and of course, the last dragon.