The main character is the healer who gets to redo his life. There are also those who wronged him in his past life, like the cruel nobles or powerful villains who are antagonists in the story.
I'm not entirely sure as I haven't read every detail of the novel, but typically there would be the healer as the main character. There might also be characters who were either friends or foes in the healer's past life that play important roles in the redo scenario.
In 'redo of healer light novels', the most prominent character is Keyaru. He's the one with the unique ability to rewind time and his story of transformation from a mistreated healer to a vengeful figure is the main focus. Besides him, there are characters like Bullet, who is involved in some of the power struggles and battles in the story. And then there's Setsuna, who also plays a part in Keyaru's adventures and his pursuit of revenge.
The 'redo healer novel' could potentially revolve around a protagonist who discovers a unique power of'redo' which is linked to the concept of healing. It might be set in a fantasy world where this power is not common. The story could be about the character's journey to master this power and use it for good, like healing the sick or injured, or even mending broken relationships within the story's setting. There could also be antagonists who try to either steal this power or prevent the protagonist from using it for positive ends.