One idea could be that the male OC is reincarnated as a villain in the BNHA world but has memories of his past life as a hero. So he struggles between his new villainous identity and his old heroic values. Another plot could be that he reincarnates as a quirkless character, like Midoriya was initially, but he uses his past - life knowledge to develop unique combat skills. Or perhaps he reincarnates as a powerful hero's sidekick and has to deal with living in the shadow while trying to prove his own worth.
A possible plot for 'bnha x male oc reincarnation fanfiction' is that the male OC reincarnates into the BNHA world during a time of great chaos. Maybe there is a war between heroes and villains that has been going on for years. He has to quickly adapt to his new life and use his knowledge from his past life to try and bring peace. He could have a special quirk that was not present in the original BNHA world but was something he had in his past life, like the ability to communicate with animals. This unique quirk could help him form alliances with certain characters or gain an edge in battles.
Maybe the Knuckle Duster has a hidden backstory that the OC discovers. The OC could be on a quest to find out more about the origin of the Knuckle Duster, which could involve delving into the history of some secret organization in the BNHA world. Along the way, they form alliances with other characters and face various challenges.
Well, you could have a plot where the OC is a healer - type with a quirk that can cure any injury or illness. However, there's a catch - using the quirk drains the OC's own life force. The BNHA characters initially doubt the OC's abilities because they seem too good to be true. As the story progresses, the OC proves their worth during a major battle where many heroes are injured. They have to decide how much of their own life they are willing to sacrifice to save others, and this creates a deep emotional and moral dilemma.
Another plot could involve the OC reincarnating into an existing character's body. This would lead to a lot of internal conflict as they try to adjust to the new identity while still having memories of their past self. They could also use their new position to change the course of events in the RWBY universe.
One idea could be that the OC is reincarnated as a member of a powerful but long - lost clan in the Naruto world. They then have to discover their clan's secrets and powers while also dealing with the ongoing conflicts in the shinobi world. For example, they might find a unique jutsu that was lost with their clan.
One idea could be to create a villain OC who has the power to manipulate time in small increments. This could lead to really interesting scenarios in battles against the heroes. For example, they could slow down time just enough to dodge attacks and then speed it up suddenly to surprise their opponents.
Another interesting concept is a robot OC that was created by a villain but has a change of heart. This robot could struggle with its programming and new - found sense of morality. It might have to hide its true identity from both heroes and villains while trying to do good in the world of BNHA.
One idea could be that the male OC was a great hero in a past life. In his reincarnation, he starts having strange dreams about his past deeds. As he gets closer to the world of Percy Jackson, he discovers that his past life has some connection to an ancient prophecy that only he can fulfill. Maybe he has some latent powers from his past that start to emerge, like the ability to control a unique element that was thought to be lost in time.
Perhaps there could be a plot where a villain in the bnha world discovers a way to summon demons from the kny world. This causes chaos as the demons start attacking the cities. The heroes and the Demon Slayer Corps then have to team up. The bnha characters use their quirks to support the kny characters in battles, like Bakugo using his explosions to create distractions while the kny characters go in for the kill.
One idea could be that the students from Bnha are sent to study in the Assassination Classroom for a special mission. They have to learn assassination skills while also trying to incorporate their own Quirks into the training. Another plot could involve a villain who has abilities similar to Koro - sensei from Assassination Classroom threatening the Bnha world, and the heroes from both universes have to team up to stop him.
One idea could be that the characters from Bnha are transported to the Attack on Titan world. They could use their unique quirks to fight the Titans in ways the AoT characters haven't seen before. For example, Deku could use One for All to launch himself at Titans with incredible force.