Maybe he has some dark secrets in his past that he doesn't want to be known. For example, he might have been involved in something illegal or unethical that could damage his reputation in the world of the web novel.
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.
It can create suspense. Readers will be curious about what he is hiding and keep reading to find out. For example, it might be revealed gradually through flashbacks or other characters' investigations, which adds an element of mystery to the story.
I don't know for sure as I haven't read it. But most likely there is the player himself who is the central character. There might also be friends or foes he interacts with who play important roles in either trying to uncover his past or helping him keep it hidden.
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.
One reason could be that he doesn't want to stand out too much. In the fanfiction world, just like in the original Harry Potter story, being overly intelligent might draw unwanted attention, especially from the bad guys. He might be afraid of being targeted more if his intelligence is known.
Another reason could be that she is not fully aware of her own feelings yet. Sometimes in novels, characters are in a state of confusion about what they truly feel. So instead of expressing something she's not sure about, Alya hides it.
Perhaps Naruto is waiting for the right moment to reveal his skills for maximum impact. He could be planning a big surprise for his enemies or wants to make a grand entrance at a crucial time. For example, in a major battle against a powerful foe, he could suddenly unleash all his hidden skills and turn the tide of the battle, which would be more effective than showing them off gradually.
He might want to protect himself. If others know how smart he is, he could become a target. Enemies might see him as a greater threat and go after him more aggressively.
One reason could be self - protection. In many light novels, the world is filled with danger. If the main character reveals his full strength too early, he might attract unwanted enemies. For example, in a world full of power - hungry villains, showing off strength could make the character a target.
Another possibility is that he's being bullied. In school settings within fanfictions, bullying is a common theme. Percy might be trying to hide his face to avoid the taunts and mean looks from the bullies. He could be self - conscious about some aspect of his appearance that the bullies have targeted, like a scar or his overall look. By hiding his face, he hopes to protect himself from their cruel remarks.