Rukia could be in the harem. She has a connection with Ichigo already and her strong personality might be drawn to the power and mystery of Hollow Ichigo. Orihime is also a likely candidate. Her kind and loving nature could be what makes her want to reach out to Hollow Ichigo and be part of his harem.
Friendship is also a big theme. In many Ichigo harem fanfictions, the relationships start as friendships. For example, Ichigo could be friends with a group of people, and as the story progresses, some of those friendships turn into romantic feelings. Another theme could be the power dynamics. Given Ichigo's abilities in the original story, how he relates to those in his harem who may or may not have similar powers can create interesting plotlines. The harem members might look up to him, or they could be equals in terms of power, and this affects how their relationships develop.
One great 'Bleach Ichigo Crossover Harem Fanfiction' is 'Ichigo's Multiverse Adventures'. It has an interesting plot where Ichigo gets thrown into different universes and ends up with a harem from various anime worlds. The character development is quite good as Ichigo has to adapt to new situations and relationships.
Well, one possibility could be that Hollow Ichigo's dangerous and alluring nature attracts various characters into a harem. For example, some might be drawn to his power, while others are intrigued by his complex personality. His wild side might make for some intense and passionate interactions within the harem.
One common theme is the struggle between light and dark within Ichigo. Since it's about Dark Ichigo in a harem setting, there's often a battle within him as he deals with his relationships while having this darker side.
There are a number of Ichigo harem fanfictions that focus on the relationships between Ichigo and the various characters in a non - inappropriate way. However, it can be a bit tricky to find ones that are really good. You might want to look for those with high ratings and positive reviews. Some might explore Ichigo's relationships with his friends in a more romantic or platonic harem - like setting, which can be really interesting to read.
A good 'Bleach Ichigo Crossover Harem Fanfiction' should have a strong plot. For example, it could involve Ichigo being sent to a new world due to some powerful magic or a strange device. His interactions with the harem members should be believable and based on his character traits from Bleach, like his protectiveness and determination.
For Ichigo's harem, Orihime and Rukia are very common. Orihime with her kind heart and strong powers of healing, and Rukia being the one who introduced Ichigo to the world of Soul Reapers. In Naruto's case, Hinata and Sakura are often part of his harem. Hinata because of her long - standing love for Naruto, and Sakura being one of Naruto's closest friends.
One common plotline is that Ichigo and Naruto end up in a shared universe where they both attract a harem of female characters from their respective shows. For example, Ichigo might have Orihime, Rukia, and others in his harem, while Naruto could have Hinata, Sakura, etc. Another plotline could be a competition between them to see who can build the more impressive harem.
One popular 'dark ichigo harem fanfiction' could be 'Dark Desires of Ichigo'. It often delves into the complex relationships Ichigo has with multiple characters in a harem - like setting, with a darker undertone to the story.