One possible reason could be Naruto's natural sense of justice. He can't stand to see a child in danger, and Koyuki being a child at that time, Naruto's heroic nature kicks in. He has always been the type to help those in need.
One possibility is that the child has a unique form of sensory perception. Naruto has his own way of sensing things, and Koyuki might have some hidden senses related to her royal heritage. Combined, the child could have a super - sense that allows it to detect not only chakra but also other hidden energies or threats. Also, the child could have the ability to communicate with animals, a trait that could come from Naruto's connection to the toads and Koyuki's possible connection to the local fauna in her land.
The story could be about the child inheriting Naruto's strong will and Koyuki's grace. Maybe the child would grow up in a world that is a mix of Naruto's Konoha and Koyuki's own land. The child might struggle with the expectations of being the offspring of two such important people and have to find their own path in the ninja world or in the diplomatic relations between the two regions.
There might be a sense of indebtedness on Koyuki's part. She may constantly look up to Naruto and be willing to support him in whatever he does later in life. Their relationship could be one where Koyuki is always there for Naruto, because of what he did for her as a child.
Yes, there are quite a few. You can start by looking on popular fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'naruto and koyuki romance' and you'll find a variety of stories with different plotlines and writing styles.
There might be. A lot of fanfiction writers are creative and might have explored the idea of Naruto and Koyuki getting married. However, the quality can vary greatly. Some might focus more on the romantic aspect, while others could incorporate more action and adventure elements into the story of their married life.
There may be some very niche or inappropriate corners of the internet where such a fanfiction might exist, but it's not something that is typically promoted or easily accessible. Naruto fanfiction usually focuses on more positive aspects like character development, new adventures, or exploring relationships in a more appropriate way.
One possible theme could be adventure. The horse could be a means of transportation for Naruto and Koyuki as they embark on a journey in the Naruto world. Another theme might be friendship, where the horse becomes a part of their bond.
Often, there's the theme of self - discovery. Through their relationship, both Naruto and Koyuki might learn more about themselves. Also, loyalty is a big one. They show loyalty to each other in the face of various challenges in the fanfiction stories.
In a 'Naruto Koyuki married' fanfiction, the plot could start with Koyuki being in danger and Naruto saving her. This leads to a deepening of their relationship and they decide to get married. After marriage, they work together to improve the lives of the people in Koyuki's country. Naruto teaches the people some ninja techniques for self - defense, and they also have to deal with threats from other ninja clans who are jealous of their power and influence as a married couple.