It could be that the story focuses on how Izuku's character changes under Batman's training. Batman might teach him about the importance of preparation and having a backup plan. Izuku, on the other hand, could teach Batman about the power of hope and believing in oneself unconditionally. The fanfiction could also explore how Izuku uses the skills he learned from Batman in his own world, against villains like All for One, in a completely new and unexpected way.
Well, perhaps it could be about Izuku learning Goku Black's unique combat styles and techniques. Maybe Goku Black would push Izuku to his limits in training, helping him gain new powers and a more ruthless edge in battle.
Well, Batman had multiple trainers. One of them was Henri Ducard. He taught Batman various combat and detective skills. Another was Jean-Paul Valley, who also had an impact on his training and approach.
Well, Naruto would probably become an even more formidable ninja. Batman's skills in strategy, detective work, and various combat techniques could enhance Naruto's abilities. Naruto might learn to approach battles with more stealth and planning, rather than just relying on his brute strength and chakra. He could also pick up some of Batman's gadgets and use them in his own ninja way, like using batarangs as a new type of shuriken.
Well, Naruto would probably become an even more formidable ninja. Batman's strategic mind and combat skills could enhance Naruto's own abilities. He might learn new ways of stealth and planning, making him a more well - rounded fighter in the ninja world.
In this fanfiction, Izuku could be inspired by Batman's lack of superpowers but still being a formidable hero. He may start training in more martial arts and stealth techniques, similar to Batman. And he could even create his own set of gadgets, like grappling hooks and smoke bombs, to aid him in combat and rescue missions.
Another possibility is that in the world where Goku Black comes from, there is an enemy who follows Goku Black to Izuku's world. This enemy could be a powerful Saiyan or a being with a dark ki similar to Goku Black. They might see Izuku as a weakness in Goku Black's plan and try to eliminate him first, making them the main antagonist in the fanfiction.