Monogatari no Kuromaku ni Tensei shite

There was a globally popular game called "The Legend of the Seven Heroes." Ren cleared the sequel of that game at the fastest record in the world, and thus he obtained bonus special data. However, no matter where he looked inside the game, he could not find the data. The moment Ren was about to give up on the search, he decided to start playing the second round of the game. Suddenly, a notification message "Do you want to start a special story?" appears on the screen. When Ren chooses "Yes" without hesitation, he loses consciousness, and when he woke up, he was a baby. Could it be that he was reincarnated as one of the heroes in "The Legend of the Seven Heroes"? Ren, who thought such a thing was impossible, could not believe his ears when he heard his name from his mother's mouth. It was the name of a classmate who betrays the heroes in the middle of the story. Of course, he wishes to live in peace. But in the game, he meets a saint whose life he's supposed to take, and doesn't. Furthermore, he ends up saving a character (the boss of a great noble family) who was supposed to die. All of these things create a development that he doesn't know about... (Source: Kakuyomu, translated)