Maybe not many people are interested in creating fanfic about them. Or it could be that their storylines don't inspire much imagination for fanfiction writers.
Show their small daily interactions. For example, how they share the household chores or how they have a routine in the morning like having coffee together. These little things make the relationship seem real.
Typically, Taiga x Ryuuji fanfiction often emphasizes their opposite personalities. Taiga's feisty nature and Ryuuji's more calm and collected self create an interesting dynamic. They usually have a lot of emotional moments where they learn to understand and accept each other better.
Taiga and Ryuuji don't end up getting married in the manga. The story focuses more on their relationship development and personal growth rather than a marriage plot.
In the story, the man was saved by a passing boater. It was a close call that made him appreciate life more. Also, it led to some personal growth and reflection on his part.
Family also plays a role. His family background and how it affects his actions and decisions are often explored. It gives depth to his character and helps the readers understand why he behaves the way he does in various situations.
One common theme is the exploration of their unspoken feelings. Since they both have complex personalities, fanfictions often delve into how they gradually realize their attraction to each other.
The character development. If the fanfiction shows how Taiga and Ryuuji have grown as individuals and how that growth has affected their relationship, it makes the kiss more meaningful. For example, if Taiga has learned to be more open with her feelings and Ryuuji has become more confident, when they finally kiss, it's like the culmination of their personal journeys.
Well, a major theme is the challenges they face. Since they are young, dealing with pregnancy brings up issues like financial concerns, finishing school, and their own personal growth. Also, there's the theme of acceptance. They have to accept the new situation and their new roles. For instance, Taiga might have to accept becoming a mother at a young age, and Ryuuji has to step up as a father - to - be. There's also the theme of how society views their situation, which some fanfictions explore in depth.