Perhaps there's a magical artifact that both April and Karai are after for different reasons. They end up having to team up to get it from a common enemy. Along the way, they face many challenges together and learn to trust one another, leading to a strong bond between them.
One plot idea could be that April discovers Karai has a secret soft side. Maybe she stumbles upon Karai helping some stray animals in the sewers. This could lead to an unlikely friendship where they start to understand each other's motives better.
A great plot could involve Karai being injured and April has to take care of her without the other turtles knowing. As they spend time together, they exchange stories about their lives and how they got to where they are. This deepens their connection and makes them see each other in a new light.
One idea could be that April and Karai are forced to team up against a common enemy that threatens both their worlds. They start off distrusting each other but as they face challenges, they learn to rely on one another's skills.
One possible scenario in a fanfiction about April and Karai could be their relationship evolving from rivalry to an unexpected alliance. They start off as enemies due to their different allegiances in the TMNT 2012 universe. April, being associated with the Turtles, and Karai, with the Foot Clan. However, as they face common threats or discover shared secrets, they might begin to work together. This could lead to some really interesting character development for both of them, as they learn from each other's strengths and weaknesses.
There are also fics that play with the idea of them having to keep their relationship a secret. Given their different backgrounds, secrecy might be necessary, and this can lead to a lot of tension and drama in the stories. Also, some fics might explore how they help each other grow as individuals while being in a relationship.
Maybe in a different universe where their clans have a more peaceful co - existence. Leonardo and Karai meet during a cultural exchange of sorts between the turtles and the Foot Clan. As they learn about each other's cultures and values, they grow closer.
A possible plot for the leonardo and karai lemon fanfiction could be that there is a prophecy about their union being the key to saving their world. At first, they are reluctant and even hostile towards each other. But as they start to explore the prophecy and what it means, they begin to develop feelings. Along the way, they have to overcome the distrust of their respective groups, and their relationship blossoms as they fight for the greater good.
Their different backgrounds make them interesting. April is a human with her own set of values and skills, while Karai has a complex backstory in the ninja world. Their clash of worlds can create great tension and drama in fanfiction.
One common theme is friendship. Since they are both characters in the same universe, many fanfics explore how they could become friends despite their differences. Another theme is rivalry, as they could be seen as rivals in some aspects of the story.
One theme could be redemption. As mentioned before, Karai has been involved in the Foot Clan's wrongdoings. April could be the catalyst for her redemption, showing her that there is a better way. Another theme could be friendship against all odds. Their different backgrounds and loyalties make it seem impossible for them to be friends, but the fanfiction could explore how they overcome these barriers.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfictions from various fandoms, including Karai x April. Just use the search function on the site to look for relevant stories.
One idea could be Karai dealing with the challenges of hiding her pregnancy while still being involved in the TMNT world. Maybe she has to keep it a secret from the Foot Clan as they might see it as a weakness.