I'm not sure of a specific title off - hand, but you can often find some really cool ones on fanfiction.net. Look for ones with high ratings and lots of reviews. Usually, the ones that combine Ichigo's sword - fighting skills with Harry's magic in creative ways are the most engaging.
When it comes to the more complex plot points, the interaction between Ichigo's Hollow side and the Dark Magic in the Harry Potter universe is very engaging. For example, if his Hollow side was somehow influenced by the Dark Arts or if it could be used to fight against it in a unique way. This could lead to a whole new set of challenges and character development for Ichigo within the wizarding world.
One appeal is that it gives fans a chance to see Ichigo in new and unexpected situations. Since lemon fanfiction often involves romantic or steamy elements, it can show a different side of his character that we don't usually get to see in the main series.
One interesting plot could be a story where the reader has some sort of special power that Ichigo discovers. He then tries to help the reader control it while they also face various Hollow threats together. This creates a bond between them that goes beyond the normal hero - sidekick relationship.
First, understand the character of Ichigo Kurosaki. Know his personality traits like his determination, his sense of justice, and his protectiveness. Then, create a believable scenario for the reader character to interact with him. For example, if the reader is a new Soul Reaper trainee, how would Ichigo react? Also, focus on the relationship development. Don't rush into things. Let it grow gradually as they face challenges together.
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.
It could be a rogue Soul Reaper. Maybe someone who has turned against the Soul Society and sees Ichigo as a threat or a valuable asset. They might want to use his power to gain control over the Hollows or to overthrow the existing power structure in the Soul Society.
One possible plot could be that Ichigo is kidnapped by a powerful and unknown enemy. This enemy might be from a different realm or a secret organization within the Bleach universe. His friends then embark on a quest to find him. They might face various challenges and battles along the way as they try to track down Ichigo's location.
It could be a new character that is a combination of a dark wizard and a Hollow. This creature would be able to use both dark magic and Hollow abilities. It would target both Hogwarts students and Soul Reapers. Ichigo and Harry would have to figure out its weaknesses, which would be a difficult task as it has powers from two very different universes.