Perhaps in the fanfiction, Sesshomaru and Naruto are both after the same powerful artifact. At first, they are rivals for it, but as they face various traps and enemies while searching for it, they realize that they need to work together. Along the way, they discover that the artifact has a connection to both of their worlds and its power could either save or destroy both universes. They must then decide what to do with it once they obtain it.
A plot could revolve around Sesshomaru being intrigued by Naruto's determination. Sesshomaru decides to train Naruto in some of his own combat techniques, which Naruto adapts to his own fighting style. In return, Naruto shows Sesshomaru the value of friendship and loyalty within a village. This could lead to Sesshomaru having a change of heart about his own solitary ways. Also, they could team up to face a common foe from Sesshomaru's world that has somehow entered the Naruto universe.
One idea could be that Kagome brings chocolate from her time as a gift for Sesshomaru. He is initially suspicious but then becomes intrigued by the unique taste. Another could be a story where chocolate has some sort of magical property in their world, and Sesshomaru and Kagome have to work together to control its power while also dealing with their growing feelings for each other.
One idea could be that they are forced to team up to fight a common enemy, like a powerful demon threatening their respective territories. As they fight side by side, they gradually develop a mutual respect for each other's skills.
Perhaps Kikyo is in trouble and Sesshomaru is the only one who can save her. But in the process, he discovers a side of her that he didn't expect, like her strong will and determination even in the face of death. This could lead to a newfound respect between them and the start of an unexpected friendship or more.
One idea could be that Sesshomaru and Sango are forced to team up to fight a common enemy stronger than they've ever faced before. During their journey together, they gradually learn to respect each other's skills. For example, Sango's expertise with her weapon, the Hiraikotsu, impresses Sesshomaru. Another plot could involve Sesshomaru getting injured and Sango taking care of him in a hidden forest. This situation would make Sesshomaru see Sango in a different light and start to develop a friendship that could potentially turn into more. A third idea is that they both get transported to a strange, magical realm and have to rely on each other to find their way back home while also uncovering the secrets of the new world.
One idea could be that Sesshomaru somehow gets transported to the Harry Potter universe. He might initially be confused by the magic there which is different from his own demonic powers. He could encounter Harry and be both intrigued and a bit disdainful, seeing Harry as a young, inexperienced wizard compared to his own powerful self. But as time passes, they might have to team up to fight a common enemy that threatens both the wizarding world and Sesshomaru's own interests.
A great plot could be a crossover where Sesshomaru and Rin end up in a magical realm that is a mix of their two worlds. Here, they meet new characters who mistake them for powerful beings from their own lore. They have to work together to find a way back home while also dealing with the power struggles in this new realm. Or perhaps a plot where Rin gains some of Sesshomaru's powers accidentally and Sesshomaru has to train her to control them, which leads to a deeper bond between them as they face challenges from other demons who are envious of Rin's newfound powers.
The oc could be a young warrior who is on a quest to retrieve a powerful artifact that Sesshomaru also has his eyes on. Instead of fighting over it, they end up teaming up to face the greater evil that is also after the artifact. This could lead to some really interesting character dynamics as they learn from each other's fighting styles and ways of thinking.
One idea could be Sesshomaru arriving in Middle - earth in search of a powerful relic. He might cross paths with Aragorn and initially be seen as a threat. Another could be that he forms an alliance with the elves, as they both have an air of elegance and long - lived existence. Maybe he gets involved in the battle against Sauron, using his demonic powers in a way that surprises both friend and foe.
One idea could be a story where a powerful magic affects both Sesshomaru and Inuyasha, causing them to be in a situation where they have to deal with the unexpected pregnancies. This could lead to them having to put aside their differences and work together to understand what's happening to them. Maybe they go on a journey to find a cure or a way to handle the situation, all while facing various challenges from other demons who see their condition as a sign of weakness.
One idea could be that the baby has some unique powers that are a combination of Kagome's spiritual powers and Sesshomaru's demon abilities. This could lead to various adventures as they try to protect the baby from those who might want to use its powers for evil.