Perhaps there could be a story where the dark forces in Mortal Kombat are trying to corrupt the pure - hearted characters in Street Fighter. Akuma might be a target for this corruption. The Mortal Kombat villains could offer him more power in exchange for his loyalty. The other Street Fighter characters would then have to try and save Akuma from this dark influence, and they might seek help from some of the more morally ambiguous Mortal Kombat characters.
A cool plot could involve Akuma from Street Fighter accidentally being transported to the Mortal Kombat realm. There, he's seen as a new threat, and Sub - Zero decides to take him on. But during their fight, they realize that there are greater forces at work trying to start a war between the two realms. So instead of fighting each other, they join forces, along with other fighters like Ken and Johnny Cage, to stop the real enemy that wants to see both worlds destroyed.
One idea could be that Naruto characters are transported to the Street Fighter universe and have to learn the fighting styles there. For example, Naruto might be intrigued by Ryu's Hadoken and try to incorporate it into his own Rasengan. Another could be a tournament where both Naruto and Street Fighter characters compete. Sakura could face off against Chun - Li, with Sakura using her medical ninjutsu in unique ways during the fight.
A possible plot for Mortal Kombat X Mileena fanfiction is her journey to discover the origin of her tarkatan side. Maybe she goes on a quest to find a cure or a way to control it better. This could lead to her encountering various characters from different realms who either help or hinder her progress. She might also have a romantic sub - plot with a character who accepts her for who she is, flaws and all.
Perhaps the OC is a time - traveler. They come from a future where Kitana's actions in the present have led to a dark future for her realm. The OC has to convince Kitana to change her path. At first, Kitana is skeptical of this strange person from the future, but as she sees evidence of the future they describe, she starts to listen. This could lead to a complex relationship where they both learn from each other and work together to change the future.
Maybe the OC has a special power that is connected to Raiden's in some way. For example, the OC can control a different aspect of electricity. Their powers start to interact in unexpected ways, which draws them closer. They could then team up to fight against a powerful sorcerer who is trying to steal their powers and use them for evil in Mortal Kombat. This would involve a lot of action scenes and also some tender moments between them.
One idea could be that the OC is a new fighter in the Mortal Kombat tournament. As they progress, they attract the attention of various characters from different realms who then form a harem around the OC. Maybe the OC has a unique power that intrigues them all.
Title: 'The Clash of Titans: MK vs Street Fighter'. In this fanfiction, Ryu from Street Fighter finds himself in the Mortal Kombat realm. He's shocked by the brutal nature of the battles there. He meets Scorpion, and at first, they are hostile. But as they realize they both fight for justice in their own ways, they decide to team up against a common enemy, Shang Tsung, who has plans to invade both their worlds. They combine their fighting styles, Ryu's Hadoken mixing with Scorpion's Spear, creating a new and powerful attack to defeat Shang Tsung.
One idea could be that the heroes from My Hero Academia are transported to the Street Fighter universe. They could participate in the Street Fighter tournaments, with their quirks adding a new dimension to the fights. For example, Deku could use his One For All to perform amazing acrobatic attacks.
One idea could be a story where Ryu and Chun - Li are forced to team up for an underground fighting tournament that has a mysterious organizer. They start off not getting along well because of their different fighting styles and philosophies. But as they face tougher opponents together, they begin to respect each other more and learn from one another.
One idea could be an OC who is a hybrid of two different Mortal Kombat races. They struggle to find their place in the brutal world of Mortal Kombat. Another could be an OC with a unique fighting style that combines different known styles in the game. For example, a mix of Scorpion's hellfire moves and Sub - Zero's ice powers.