Boruto could be developed by showing his growth in responsibility. For example, in the fanfic, he could take on the task of teaching Himawari a new jutsu. This would not only show his skills but also his patience. Himawari, on the other hand, could be developed by showing her becoming more independent. Maybe she decides to go on a small mission on her own to prove herself to Boruto.
One great 'Boruto and Himawari fanfic' is 'Sibling Adventures'. It shows their daily life in Konoha, with Boruto teaching Himawari some new ninja techniques in a really cute way. They also have some small adventures together around the village, like finding a lost pet. Another one is 'Himawari's Growth' which focuses on Himawari's development as a ninja under Boruto's guidance. It's really inspiring to see their bond strengthen as she learns.
One great idea for a Boruto and Himawari fanfic is a story where they go on a journey outside the village. They might encounter new types of ninjas or strange creatures. Himawari could be the one to sense danger with her Byakugan first, and Boruto would be ready to fight. It would show their growth as ninjas and also their bond as siblings.
Perhaps in the fanfic, Boruto and Himawari are involved in a festival in the village. They enter a contest together, like a ninja skills show - off. Boruto is a bit overconfident at first, but Himawari keeps him grounded. In the end, they learn more about each other and their combined strength as siblings.
The relationship can be shown as a strong sibling bond. For example, Boruto could be protective of Himawari when she is in danger during a mission. Or Himawari could be the one to cheer Boruto up when he is feeling down about his ninja training.
The theme of family also plays a big part. Many fanfics involve their parents, Naruto and Hinata, and how the family dynamic affects Boruto and Himawari. Adventure is another common theme. They might go on a journey to discover a new ninja technique or to help a neighboring village. It makes for exciting reading.
One idea could be a story where Boruto and Himawari discover an old diary of Naruto's from his early days as a ninja. Hinata helps them understand the context and the values their father held. They then use those lessons to face a new threat in the village.
Well, obviously Naruto and Hinata should be included. Naruto could offer some words of wisdom to Boruto and Himawari as they face different challenges. Hinata can be the nurturing mother figure who is always there for them. Another great character to include could be Sasuke. He could train Boruto and Himawari in some new ninja techniques.
Some fanfictions might explore a future where Boruto and Himawari are older and have important roles in the village. For instance, Boruto could be leading a major mission and Himawari is in charge of the village's defenses in his absence. The story could detail their responsibilities, how they handle the pressure, and how they still maintain their close connection despite their busy schedules.
One idea could be a story where Himawari and Boruto go on a secret adventure together outside the village. They encounter a strange new jutsu and have to figure out how to deal with it, relying on their unique sibling bond.