One idea could be Ichigo crossing over into a different anime universe like the Naruto world. He could meet Naruto and they'd team up against a common enemy. Maybe a powerful new threat that combines the powers of Hollows and the Tailed Beasts.
Another plot could involve Ichigo in a crossover with the world of One Piece. He might end up on the Grand Line and have to deal with pirates while also trying to find a way back to his own world. He could form an alliance with Luffy and his crew, and his Soul Reaper powers would be a huge asset during battles at sea.
Well, a cool crossover fanfiction could be with the DC universe. Imagine Ichigo meeting Superman. They would surely have different views on justice. Superman is all about truth, justice, and the American way, while Ichigo is more about protecting his friends and the spirit world. Their meeting could lead to some intense debates and also team - ups against powerful villains.
Aizen Sousuke would be an interesting crossover character. Since he's so powerful and manipulative in the Bleach universe, seeing him in a different setting with Ichigo could create some really complex and intense storylines. They could be forced to work together against an even greater evil in a crossover universe.
Well, a plot could involve Ichigo being turned into a vampire against his will. He then has to deal with the internal conflict of his human morals versus his new vampiric instincts. He might find that some of his friends are scared of him, while others are determined to help him find a way to reverse the transformation. And there could be a love interest who accepts him despite his new nature, adding a romantic sub - plot to the story.
One idea could be Ichigo getting trapped in a virtual reality game world where he has to fight his way out using his Soul Reaper powers. Another could be a crossover where Ichigo teams up with other game characters to defeat a powerful in - game boss.
One idea could be that Ichigo has to hide his vampire nature from his friends at first. He struggles with the new instincts and powers, like enhanced speed and strength. Maybe he has to resist the urge to drink blood from his loved ones.
One interesting character to crossover with Ichigo is Light Yagami from Death Note. The clash between Ichigo, who is a protector, and Light, who is a morally ambiguous character with the power to kill, would be very engaging. Saitama from One - Punch Man could also be a great choice. Saitama's overpowered nature and Ichigo's journey to become stronger would make for an interesting story. And what about Alucard from Hellsing? His vampire powers and Ichigo's powers related to the afterlife would create a really dark and exciting crossover.
One idea could be that the OC has a special power that only activates when in close proximity to Ichigo. For example, the OC can sense Hollows from a great distance, which helps Ichigo in his battles against them.
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.
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.