Another option is a crossover with a post - apocalyptic world. The garou's survival instincts and combat abilities would be well - suited for this harsh environment. It could either be a lone wolf trying to survive or join a group of survivors, bringing its own set of skills and challenges to the group.
Another plot could involve a crossover with a different anime universe through a strange portal. For example, if he entered the world of My Hero Academia. Garou could initially try to assert his dominance but quickly realizes that the quirks in that world are different from his martial arts skills. He might then start to learn about these new powers and how to adapt, all while causing chaos and also forming unexpected alliances.
One idea could be a Garou OC who is a lone wolf, not part of any pack, and has to survive in a world full of both human and supernatural threats. They could have unique powers like the ability to blend into shadows, which helps them in their solitary existence.
One idea could be a story where Garou and Metal Bat are forced to team up against a common enemy stronger than they've ever faced. They start off hating each other but gradually learn to respect each other's fighting styles.
One idea could be exploring Garou's past more in - depth. Maybe show his childhood and what led him to become the way he is. Another could be a story where Garou has to team up with Saitama for some strange reason, like an even more powerful enemy emerging. Or perhaps a fanfiction where Garou tries to train under Saitama to become stronger in a different way than his usual self - taught methods.
One idea could be that they start off as rivals but are forced to team up against a common, even more powerful enemy. As they fight side by side, they gradually gain respect for each other's fighting abilities.
One interesting idea could be a crossover with "Moana". Elsa's ice powers and Moana's connection to the ocean could create a really cool dynamic. Maybe Elsa accidentally freezes part of Moana's ocean and they have to work together to fix it. Another could be with "Tangled". Rapunzel's long hair and her adventurous spirit combined with Elsa and Anna's journey in Frozen 2 would be exciting. Rapunzel could use her hair to help them climb mountains or cross chasms. A third idea is a crossover with "Beauty and the Beast". Belle's love for books and knowledge could help Elsa understand more about her powers and the history of magic in the Frozen world.
A Thundercats and Star Wars crossover fanfiction would be really cool. The Thundercats could be in the Star Wars universe, and their unique powers and weapons could be a great addition. Maybe the Thundercats could help the Jedi or the Rebels in their fight against the Sith or the Empire. For instance, Cheetara's speed could be useful in battles, and Tygra's illusions could be used to deceive the enemy.
For a good character interaction between Garou and Saitama, start with their fundamental differences. Saitama is a hero who is bored with the lack of challenge, while Garou hates heroes. Have them start with a fight, but make it a comical one where Saitama's nonchalance annoys Garou to no end. This can lead to some great dialogue exchanges where Garou tries to taunt Saitama into taking him seriously, but Saitama just doesn't care.
Start with an interesting hook. Maybe it's a sudden appearance of the garou in a world that has no idea what it is. This could create immediate tension and curiosity. Then, gradually introduce the background of the garou as the story progresses. You can also start by creating a profile for your garou character in the context of the crossover. Decide on its personality, goals, and how it will change throughout the story.
A Digimon and Sailor Moon crossover is an interesting concept. The Digimon could help the Sailor Scouts in their battles against the Dark Kingdom. The magical powers of the Sailor Scouts combined with the digital powers of the Digimon would create a really unique and exciting story. And a Digimon and Avatar: The Last Airbender crossover. The Digimon could be part of the different nations, and they could use their abilities to help Aang and his friends in their quest to restore balance.