Shirou could fit in as a mentor figure. His experience in combat and his strong sense of justice could make him a great teacher for Sakura. He could help her understand the importance of protecting the world not just from the Clow Cards, but from any potential threats.
There could also be a fanfic where Shirou and Sakura are part of a team in a tournament. They have to use their combined skills - Shirou's combat and tracing abilities and Sakura's cardcapturing skills - to defeat other powerful opponents. This kind of fanfic would be full of action and strategic battles, as they figure out how to work together best.
Shirou would fit in as a powerful and unique addition. His combat skills and magecraft would make him a formidable ally or opponent. He could use his projection abilities to create various weapons and tools, which would be very useful in the battles that often occur in the Highschool DxD world.
In fanfiction, Shirou Emiya could be integrated into the Highschool DxD world by being a wildcard factor. For example, he could be a human with powers that no one expected. His strong sense of justice would lead him to get involved in the conflicts between the different supernatural groups. He might even form his own group of allies, made up of both normal students and supernatural beings who believe in his cause.
One way Shirou Emiya's abilities could fit is through his projection magic. In the MHA world, it could be seen as a form of quirk where he can project weapons. This would make him a unique combatant, similar to heroes like Snipe who use ranged weapons. He could use his projections to quickly adapt to different battle situations, for example, projecting a shield when facing a powerful ranged attack or a sword for close - quarter combat.
Shirou Emiya's abilities would have an interesting adaptation in the Fairy Tail universe. His tracing magic could be related to the concept of analyzing and replicating magic in Fairy Tail. He might be able to study the magical auras of different spells and then create his own versions. His Reality Marble, Unlimited Blade Works, could be a very high - level form of spatial magic in the Fairy Tail context. It could be seen as a pocket dimension where he stores all the weapons he can project. In battles, he could use this ability to surprise his opponents. For example, he could suddenly pull out a large number of weapons from his Reality Marble during a fight, much like how some Fairy Tail wizards can summon multiple magical items or creatures. Also, his skills in swordsmanship would be highly valued in a world where melee combat is also an important part of magic battles.
Shirou's projection magic could be really interesting in the Rosario Vampire world. He could project weapons that are effective against the various supernatural beings there. For example, if there are werewolves, he could project a silver - edged sword.
His projection magic might be affected by the different magical rules in the Highschool DxD world. Maybe it becomes more powerful or has some new limitations. For example, projecting holy swords could have a different energy cost or be more effective against certain types of devils or fallen angels.
One great Shirou Emiya time travel fanfiction could be about him going back to the Fourth Holy Grail War. He might use his knowledge from the future to change certain events, like trying to prevent some of the tragedies that occurred. This could lead to a whole new chain of events in the Fate universe.
Well, it's very likely. Since Naruto and Shirou Emiya come from two different yet highly popular anime/manga universes. Fans love to create crossovers in fanfiction to see how characters from one world would interact in the context of another. Some of these fanfics might be really well - written and offer interesting takes on how Naruto could be like Shirou Emiya, perhaps in terms of their personalities, goals, or even their powers if some creative liberties are taken.
When writing a Cardcaptor Sakura sister fanfiction, it's important to keep the magical elements consistent with the original. For example, if you introduce new cards, they should fit within the existing magic system. Also, explore the emotions between the sisters. Maybe there's some jealousy or admiration that can be developed into a great story. You can start with a simple idea, like the sister accidentally getting involved in one of Sakura's card - capturing missions and then build on that.