No. Writing sexual fanfic involving underage or inappropriate relationships in the Naruto universe is completely unethical and violates the basic principles of respect for the source material and its intended audience, which often includes children and young fans.
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.
No. The official Boruto series is focused on the growth of Boruto, his friends, and the new generation in the ninja world. Fanfics are often creative interpretations by fans, but this one sounds like it's not in the spirit of the official series at all. It's likely a non - official and inappropriate creation that has no place in the official Boruto story.
It is highly inappropriate. Such content not only goes against the values that should be upheld in the fan community but can also be considered a form of child exploitation if the characters are minors. Fanfiction should focus on creativity in a positive and respectful way.
One alternative could be writing about their adventures together. For example, they could go on a mission to explore a mysterious land or fight against a new and powerful enemy. This would focus on their skills and cooperation.
For Boruto, he could develop from being a bit overconfident to a more mature and reliable ninja. Maybe through his interactions with Sumire, he learns to think more before acting. For Sumire, she could become more assertive. Working with Boruto, she might find the courage to voice her opinions more often and take on more leadership roles.
Boruto's reaction would be complex. He'd be heartbroken, for sure. He might start to question his own worth and purpose. But over time, he'd realize that he has to carry on Naruto's legacy. He'd become more serious and focused. He'd also become more empathetic towards others, understanding the weight of sacrifice. He might even start to study Naruto's techniques and leadership style more closely, trying to emulate the things that made Naruto such a great Hokage and hero.
It could be the Kara organization. They've been shown to be interested in Boruto's Karma mark in the original series, so they might have finally made a move to abduct him in the fanfic.
In a 'naruto dies boruto fanfic', Boruto's character would go through a major transformation. He would be forced to grow up overnight. Initially, he might be consumed by anger and a desire for revenge if Naruto was killed unjustly. But as time passes, he would learn to channel that energy into positive change. He would study his father's leadership style and try to implement it in his own way. He would become more diplomatic, forging alliances with other villages to strengthen Konoha's position. His sense of justice would be refined, and he would be more committed to protecting the world his father loved so much.