Naruto might feel a sense of responsibility. He would see it as his duty to help Boruto understand and control the Jougan. So, he could start to create special training regimens for Boruto. These regimens would be designed not only to strengthen Boruto's physical and ninja skills but also to help him master the unique powers that come with the Jougan. He would also teach Boruto about the importance of using such power for good and protecting the Hidden Leaf.
In fanfiction, if Naruto discovers Boruto's Jougan, it could change the power dynamics in the Hidden Leaf. Naruto would likely be both proud and worried. Proud because his son has such a unique and potentially powerful ability, but worried because it might attract unwanted attention. He could start to share his own experiences with dealing with unique powers more openly with Boruto. This might include stories about how he tamed the Nine - Tails' power. He would also probably consult Kakashi, his former teacher, to get some insights on how to guide Boruto in harnessing the Jougan's power safely and effectively.
First, do some research on the Jougan. Know what it can do in the Naruto universe. Then, create a main character who has the Jougan. Decide on their personality, like if they're a shy person who is suddenly thrust into power. Next, come up with a basic plot, such as the character has to use the Jougan to save their village from a new threat.
Yes, there are. You can find Naruto has Jougan fanfictions on various fanfiction platforms like FanFiction.net and Archive of Our Own. Just search for 'Naruto has Jougan' on their search bars.
Naruto would be devastated. He might blame himself for not being able to protect his son. Sasuke would be angry and would likely go on a hunt for the perpetrator. His friends like Sarada and Mitsuki would be heartbroken. Sarada might vow to become stronger to prevent such a tragedy from happening again.