Perhaps an ancient artifact in the MHA world has the power of the Naruto toads sealed within it. A villain discovers it first but a young hero - in - training manages to steal it away. Once in their possession, they unlock the toad quirk. They would then need to train hard to master it, just like Naruto did. They could call on the toads for help in battles, use their strong physical attacks and even learn some of the toad - related ninjutsu, adapting it to fit the rules and physics of the MHA world.
They would be very powerful. Just like Naruto can summon giant toads, this character could summon toads in the MHA world. They could use the toads as mounts or have them fight alongside. For example, they could have a toad use its tongue to grab villains and hold them in place.
Tsuna's quirk, if we assume his Dying Will Flames are his quirk in the MHA universe, would likely be classified as an emitter type quirk. He could use his X - Burner attack as a long - range offensive move against villains. His hyper intuition could also be a part of his quirk, allowing him to predict his opponents' moves in battle. This would make him a valuable asset in hero teams, especially in complex battles where strategy is key.
He could have a quirk like 'Enhanced Intellect', which would further boost his already incredible detective skills. This would make him able to analyze situations even faster and come up with strategies on the fly.
Revenge is also a prevalent theme. Maybe they or someone they love has been wronged in the past. So, they embark on a journey to seek revenge. However, as the story progresses, they might also find a higher purpose like reforming society rather than just getting personal vengeance.
A good book about non-fiction vigilantes would present a balanced view. It should show both the positive and negative consequences of their deeds. And it should provide historical and social context to explain why they emerged.
His quirk could be something like super - speed regeneration. In the original Naruto series, he has a great deal of stamina and the ability to heal relatively fast. But with this quirk, he could recover from even the most severe injuries in seconds. This would mean he could keep fighting no matter how badly he was hurt, and his enemies would find it extremely difficult to defeat him.
I'm not sure about a specific 'josuke x koichi fanfiction' off the top of my head, but you can try searching on fanfiction - specific websites. Usually, those sites have rankings and reviews which can help you find high - quality ones.