One idea could be Ichigo getting transported to a different dimension where he meets various female characters from different anime. They all fall for his unique powers and his sense of justice. For example, he could meet a magical girl who is intrigued by his sword skills and a strong - willed ninja girl who admires his courage.
A possible plot is that Ichigo is on a mission in a new world and he keeps saving different girls. These girls then form a harem around him. Each girl has her own backstory and reasons for being attracted to Ichigo. There could be a shy girl who is in awe of his strength, a feisty girl who likes his rebellious side, and a more mature girl who respects his leadership skills.
Maybe in the fanfiction, Ichigo accidentally creates a harem when a spell gone wrong makes several female characters have strong feelings for him. These characters could be from different species like a vampire girl who is attracted to his strong reiatsu and a mermaid who sees his kindness. They all compete for his attention in a comical and sometimes dangerous way.
One idea could be Ichigo being transported to a different anime world where he meets a harem of characters from that world. For example, if he ended up in the Naruto world, he could encounter female ninja who are intrigued by his unique powers and personality. Another plot could involve a magical spell that accidentally creates a harem situation for Ichigo in his own Bleach world, with various female characters suddenly having strong feelings for him. Maybe there's a time - travel element where Ichigo goes back in time and gathers a harem of historical figures with spiritual powers.
One plot idea could be that Ichigo, with his unique powers, gets transported to the Naruto world. The girls in Naruto's world are intrigued by his different abilities and his cool demeanor. For example, Sakura might be interested in his healing powers which are different from the medical ninjutsu she knows. Another could be a tournament where Ichigo has to fight using Naruto - style combat and in the process, he catches the eye of the female ninjas. They start to form a sort of harem around him as they want to learn from him and befriend him.
One idea could be Ichigo getting transported to different anime universes where he meets various female characters who are instantly attracted to his unique powers and sense of justice. For example, he could end up in the Naruto universe and meet Hinata, and she might be intrigued by his ability to see spirits. Another could be in the One Piece world, where Nami sees Ichigo as a potential ally against powerful enemies. The harem aspect would develop as these characters start to compete for Ichigo's attention in different ways.
One idea could be to have Ichigo cross over into a different anime universe filled with potential love interests. For example, he could end up in a magical girl anime world where he has to deal with a group of girls who are both intrigued by his power and his different nature. Another could be a crossover into a post - apocalyptic world where a harem of strong - willed women see Ichigo as a symbol of hope and gradually develop feelings for him.
One possible plot idea could be how Ichigo deals with the impending fatherhood in a harem situation. He might struggle to balance his relationships with all the women in his harem while also preparing for the new arrivals. Another could be the reactions of the other harem members to the pregnancies, whether it's jealousy, support or a combination of emotions.
One idea could be that Mugetsu Ichigo finds himself in an alternate universe where he has to team up with his other - self from that universe to defeat a powerful new enemy. Maybe this enemy has the ability to nullify his Zanpakuto powers, forcing him to rely on new and creative combat strategies.
Maybe in a Fullbring Ichigo crossover fanfiction, Ichigo's Fullbring could somehow get mixed up with a magical artifact from another fictional realm. This causes him to gain new and unpredictable powers. He then has to journey through different dimensions to find a way to control these powers while also being chased by powerful enemies who want the artifact for themselves.
One plot idea could be that Ichigo somehow gets transported to the FMA world. He might initially be confused by the alchemical rules but then use his Soul Reaper powers in unique ways. For example, his Zanpakuto could be seen as a form of alchemical weapon, and he could fight alongside the Elric brothers against the homunculi. Another idea is that the Philosopher's Stone has some connection to the Hollow within Ichigo, and characters from both universes have to work together to prevent a catastrophic event.
One idea could be that Ichigo discovers he has hidden Quincy powers that are much stronger than he thought. This could lead to him having to train with Quincy mentors to control it, while also dealing with his Soul Reaper duties.
A cool plot could be that there's a magical artifact that has the power to grant any wish. Ichigo and Erza both hear about it independently and end up chasing it. When they meet, they initially think the other is an enemy. But as they start to understand each other's motives, they decide to share the wish if they get the artifact. However, they face many challenges along the way, like traps set by other people who also want the artifact. Erza's strategic mind and Ichigo's determination would be great assets in this adventure.