It could also be related to a prophecy or a pre - determined fate in the fanfic's plot. There might be some kind of dark prophecy that says Kawaki has to kill Naruto to prevent a greater evil. Or perhaps Kawaki is being controlled by an external force that has a vendetta against Naruto and uses Kawaki as a tool to carry out the murder.
One common theme is friendship. Writers often explore how Himawari and Kawaki, who come from different backgrounds, form a bond of friendship. Another theme is growth. They both grow as characters, learning from each other.
Kawaki makes his appearance in Boruto manga at a specific point, but I can't recall exactly. You might want to check the official manga sources for the precise chapter.
An 'abusive mitsuki bakugou fanfic' is likely a fan - created fictional story involving the character Mitsuki Bakugou in an abusive situation. Fanfics are written by fans of a particular work, in this case, probably related to the My Hero Academia series where Bakugou is a character. However, such content might be disturbing as it involves abuse.
In Sarada and Mitsuki fanfiction, there are various storylines that can be explored. One common theme could be their friendship growing stronger as they face different challenges in the ninja world. For example, they might go on a mission together and learn to rely on each other's unique abilities, like Sarada's Sharingan and Mitsuki's snake - like skills.
One common theme is growth. Both Himawari and Kawaki are often depicted as growing both as individuals and in their relationship. Another theme is acceptance. Since they come from different backgrounds, fanfictions usually show how they accept each other's differences.