Don't engage with it further. Instead, focus on the vast amount of positive Naruto fanfiction out there. There are many great stories that explore the characters' development, their battles, and their emotional bonds in a healthy and respectful way. You can also join fan groups that are dedicated to positive Naruto content creation and discussion, and help spread the word that this kind of inappropriate content has no place in the Naruto fandom.
If one accidentally comes across such a story, they should immediately stop reading or watching it. It is not something that should be consumed casually. Then, they could consider reporting the source if it is inappropriate or offensive content.
Because it's immoral. It involves a serious violation of a character's dignity and promotes a negative and harmful view.
Immediately close the page or source where you found it. Do not engage with it as it is likely to be inappropriate and against ethical and legal norms.
You should immediately distance yourself from it. Report it if it is being spread in an improper way as it is likely to be unethical content.
You should avoid it. Such content is not in line with the values of the original story and can be offensive. Look for more positive and appropriate fanfics instead.
Ignore it.
First, don't engage further with those stories. Then, talk to your wife about it. Let her know what you've seen and make sure she is aware of the situation. You might need to work together to find out where these stories are coming from and how to deal with the people spreading them if it's a case of slander.
If you come across such fanfiction, it's best to just move on and not engage with it. It may be a sign of a more disturbing or inappropriate take on the character that doesn't align with the positive aspects of the Hetalia fandom.
You should immediately look away and avoid engaging with such inappropriate content. Respect your partner's dignity and privacy.
If you accidentally come across it, close the page or source right away. You can also choose to report it if it's in an inappropriate place. It's important to stay away from this type of inappropriate content.