Perhaps it could be the school bully. This bully might be jealous of Vegeta's strength and popularity among some students, and also of Bulma's intelligence and charm. So, he tries to create problems between them, like spreading false rumors or trying to sabotage their school projects.
It could also be an ex - boyfriend of Bulma who still has feelings for her. He doesn't like seeing Bulma with Vegeta and tries to win her back by causing trouble. He might lie to Vegeta about Bulma's intentions or try to make Bulma feel guilty for moving on with Vegeta.
Frieza or his remnants could be antagonists. They might see the unborn child as a potential threat in the future, especially if it has strong Saiyan powers. So they could plan to attack Bulma to prevent the birth.
In a vegeta x bulma high school fanfiction, it could be that there is a school dance coming up. Bulma is determined to go with the most popular guy in school, but Vegeta, who has a secret crush on her, decides to enter a dance - off to win her over. Along the way, they face challenges from jealous classmates and misunderstandings, but in the end, they realize their true feelings for each other.
There could be a rogue Saiyan who has different ideals from Vegeta. This Saiyan might think that the baby should be raised in a more traditional, warrior - like way and try to take the baby from Bulma and Vegeta. Or, an evil scientist who wants to experiment on the baby's unique Saiyan - human DNA could be the main antagonist, creating all kinds of challenges for Vegeta and Bulma to protect their child.
At first, they might be at odds. Vegeta could be seen as cold and aloof, while Bulma is more outgoing. Bulma might try to befriend Vegeta, but he brushes her off. However, as time goes on, he starts to respect her intelligence when she helps him with a difficult class assignment.
If Vegeta and Bulma met in high school in fanfiction, their relationship development would be quite a journey. Initially, Vegeta's cold and aloof attitude would put Bulma off. She might think he's just a bully. But as she gets to know him better, she realizes there's more to him. Maybe she discovers his past and his reasons for being so guarded. Meanwhile, Vegeta starts to respect Bulma's tenacity and her ability to stand up to him. They could start sharing secrets, like Vegeta telling Bulma about his Saiyan heritage. This new - found trust could lead to them spending more time together outside of school. They might go on adventures, exploring the outskirts of town or looking for strange phenomena. As they face challenges together, their bond would strengthen. Their relationship would be a mix of bickering, like when Bulma teases Vegeta about his Saiyan eating habits, and deep, heartfelt conversations. Eventually, they would become inseparable, and their relationship could evolve into a loving and committed one.
They could develop a love - hate relationship at first. Vegeta might think Bulma is too nosy and talkative, while Bulma could see Vegeta as a rude and arrogant guy. But then, as they spend more time together, like when they are in the same club or study group, they start to see the good in each other.
Sometimes new, original antagonists are created for dark fanfiction. They could be powerful demons or shadowy figures from Vegeta's past on Planet Vegeta. These antagonists might have vendettas against Vegeta and see harming Bulma as a way to get revenge. They can bring in elements of mystery and horror to the story.
Well, in this high school setting in fanfiction, Bulma could be the popular girl who is into science and technology. When she meets Vegeta, who is probably the new and mysterious transfer student. Their first encounter could be a clash of personalities. Vegeta might be dismissive of her at first, but Bulma's determination to get to know him better could lead to an interesting friendship or even more. Maybe she tries to figure out his strange powers, and that draws them closer.
In this kind of fanfiction, they might start off as rivals. Vegeta's proud and competitive nature could clash with Bulma's intelligent and headstrong personality. Maybe they get paired for a science project and initially bicker all the time but gradually start to understand each other.
Their relationship could develop slowly. At first, they might just be classmates who notice each other's unique traits. Goku would notice Bulma's intelligence when she answers difficult questions in class. Bulma would notice Goku's physical abilities during gym class. As they start to interact more, like working on a group project together, they'd find out they complement each other well.