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.
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.
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.
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.
One great 'bleach ichigo mugetsu fanfic' could be 'The Power of Mugetsu Unleashed'. It really delves into Ichigo's transformation and the implications of his Mugetsu form in a unique way. It has some intense battle scenes and also explores the emotional turmoil Ichigo goes through.
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, 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.
The story could then develop as Ichigo tries to find a way back home. Along the way, he gets caught up in the politics and battles of the DxD world. He might meet Issei and initially be at odds with him because of their different outlooks on power and combat. But as they face common enemies, they start to work together. Ichigo could also have run - ins with powerful devils like Sirzechs Lucifer, who might be intrigued by his power and want to either recruit him or eliminate him as a potential threat.