Well, I know it's late to do it now, but let's do it anyway. It can reduce some confusion at least. I am introducing this now because all the characters were not introduced during the early chapters and it would have also ruined the suspense. So, I hope you will forgive this poor author.
Character introduction: -
Rio Flash:
Characteristics: Dark Black Pupils and Hair. Expressionless and ordinary face.
An individual reborn as an extra in the novel Rio read in his previous life. His friend gave him that book and read it casually just like he has been doing always been. But when he woke up the next day, he found himself in the body of Rio Flash.