One common theme is the idea of unexpected change. The pregnancy is an unplanned event that shakes up the characters' lives. Another theme could be love and support. Raku and Chitoge might have to show their love for each other in new ways as they face this big change. Family also often plays a role, with their families having different reactions to the pregnancy.
Well, in such a fanfiction, the pregnancy might be a result of an accident. Chitoge could be worried about how it will affect her relationship with Raku. Maybe she tries to hide it at first. But as the story progresses, things start to come out. Their friends like Kosaki might have different reactions, adding more drama to the plot.
For Raku, he could be developed further by exploring his insecurities more deeply. In the original story, he's often caught up in the love polygon, but we could see him face his own self - doubt about whether he's worthy of Chitoge's love. This could make his character more relatable.
Another plot could involve a time - travel aspect. Raku and Chitoge could be sent back to a time when their families first had the feud. They could try to prevent the feud from starting, which would change the course of their relationship in the present. This would give them a chance to get to know each other without the burden of the arranged marriage plot.
The plot is crucial. It should be engaging and not just focus on the pregnancy alone. Maybe there are some family reactions to deal with, or how their relationship changes because of the pregnancy. Also, the writing style matters. A vivid and descriptive writing style can really bring the story to life, making the readers feel as if they are part of Raku and Chitoge's world during this important time in their lives.
Well, another place could be Tumblr. There are a lot of fans on Tumblr who create and share fanfiction. Use relevant tags like #RakuChitoge #PregnancyFanfiction. However, the content on Tumblr can be a bit scattered, so you might need to do some digging. But it's definitely a good source if you're looking for unique takes on the Raku and Chitoge pregnancy concept in fanfiction.
One idea could be a crossover where Naruto characters end up in the world of Nisekoi. For example, Naruto could meet Raku and they team up for some sort of mission in the Nisekoi city. It would be really cool to see Naruto's ninja skills in that setting.