If creating a new character in this fanfiction, let's say a student who is influenced by Mugetsu Ichigo. Their arc could start with being in awe of Ichigo's power. Then, through facing challenges together, they develop their own strength and identity, independent of just idolizing Ichigo.
In a 'mugetsu ichigo highschool dxd fanfiction', a character arc can be created by putting characters in situations that force them to change. For Mugetsu Ichigo, it could be his struggle to adapt to the different rules and values in the High School DxD world. This internal conflict can lead to him evolving, whether it's in his fighting style or his relationships with others. For other characters, like the devils in the school, their arcs could be about re - evaluating their views on this new and powerful entity (Ichigo) that has entered their world.
The plot could involve Ichigo's unique abilities causing a stir in the Highschool DxD world. Since he has the power of Mugetsu, he could be a target for some groups who want to either use his power or get rid of him. And at the same time, he could befriend some of the characters from DxD and they could learn from each other's powers.
One idea could be that Mugetsu Ichigo somehow ends up at the High School DxD school and has to deal with the different factions there. He might use his unique powers to solve some of the school's problems.
He could fit as a powerful outsider. His power level is extremely high with Mugetsu, so he'd be a force to be reckoned with. Maybe he'd be seen as a wildcard by the different groups in DxD.
Rias Gremory would also be an interesting character to focus on. If she were to interact with Ichigo, her leadership skills and her own goals within the Highschool DxD world could be influenced. Maybe she tries to recruit Ichigo for her peerage, which would lead to all sorts of conflicts and negotiations.
First, you need to understand the characters well. For Ichigo, know his personality traits like his determination and his sense of justice. For the Highschool DxD characters, understand their hierarchies and their goals. Then, come up with a unique plot. It could be a battle - oriented story where Ichigo and the DxD characters fight a powerful enemy together. Or it could be a more slice - of - life story where Ichigo adapts to the strange new world of DxD.
Ichigo could be a game - changer. His Hollow - like powers might be mistaken for some sort of demonic or otherworldly ability in the Highschool DxD setting. This could lead to both misunderstandings and interesting interactions with the characters there.
One possibility could be that Ichigo's powers would make him a very unique and powerful character in the Highschool DxD universe. His zanpakuto abilities and high - level combat skills could give him an edge in the battles against the devils and other supernatural beings in that world.
A fanfiction could focus on Ichigo attending the school in Highschool DxD. His presence would surely disrupt the normal balance. He might not be interested in the whole 'devil' and 'angel' thing at first, but gradually get involved. He could also introduce some of his Soul Reaper training methods to the students there, which would be very different from what they're used to.
First, consider the world of Highschool DxD. Your OC should fit into this universe. So, if you want to make a devil OC, understand the hierarchy and politics of the devil society. For creating an interesting OC, you can also add some flaws. No one is perfect. Maybe your OC is overconfident and this often gets them into trouble. Another aspect is their relationships. They could have a complicated relationship with the main characters. For instance, they might start as an enemy of Issei but later become an ally due to shared goals. Also, give them a distinct voice in the story, which means how they speak and the words they use should be unique to them.
First, give your OC a unique backstory. For example, if your OC is a devil, they could have a tragic past that led them to become a devil. Second, think about their powers. Make them different from the existing characters in Highschool DxD. Maybe they have a special ability related to an element like ice or fire. Third, develop their personality. Are they shy, bold, or mischievous? This will make your OC stand out in the fanfiction.