The player might change the title and his name associated with the novel so that it becomes difficult to trace back to him. He could also use some legal means like copyright restrictions to limit its availability if possible.
One way could be to create a new brand or identity for himself and distance the new works from the old one. This way, people are less likely to connect the past novel with his current self. He can also work with publishers or platforms to restrict the visibility of the past novel.
Maybe he is ashamed of it. Some past works might not be up to his current standards, or perhaps there are elements in the novel that he doesn't want to be associated with anymore.
Well, you might consider using a hidden partition on your device or using specialized software that offers stealth mode for storing and accessing your story. Also, changing the file extension or compressing it with a password can add an extra layer of protection.
To hide a story, you might consider disguising it as something else. For example, presenting it as a fictional tale within a larger collection of unrelated stories. Or perhaps changing key details to make it less recognizable. Another option is to only reveal parts of it at different times to different people, so no one has the complete picture.
You could keep it to yourself and not tell anyone. Simple but it works sometimes.
You could use password-protected folders or apps. That way, only those with the password can access the stories.
You can put it in a private folder or use encryption software to protect it.
You could use a book cover or a sleeve to hide the light novel covers. It's simple and works well.
To hide clues well in a mystery novel, you might want to use misdirection. Make the reader think one thing is important when it's not, and vice versa. And place clues in unexpected places, like a passing comment or a seemingly insignificant object description.
You can make the dialogue less prominent by using smaller font size or a less bold color.
Since I don't have in - depth knowledge of this light novel, it could be that the 'player' has a dark or complicated past. Maybe he was involved in some sort of scandal or had a difficult upbringing. The story might show how his past affects his current actions and relationships within the context of the light novel's world, whether it's a virtual game world or some other fictional setting.