Maybe the Soul Society discovers the existence of the ninja world. Some of the Bleach characters, like Rukia, go to the ninja world to learn about chakra. Meanwhile, Naruto and his friends are curious about the powers of the Soul Reapers. This leads to a cultural exchange of sorts between the two groups, with some humorous misunderstandings along the way.
One idea could be that Naruto and Ichigo meet in a dimension where their powers are combined. They have to fight a new, powerful enemy that threatens both their worlds. For example, a villain who can manipulate the energy of chakra and reiatsu at the same time.
A possible plot is a tournament - style crossover. Characters from both Naruto and Bleach are invited to a special tournament in a neutral dimension. This would lead to some really exciting match - ups like Sasuke vs. Byakuya or Naruto vs. Renji. They would fight not just for victory but also to prove the superiority of their own world's fighting styles. Along the way, they might learn from each other and form unexpected alliances.
One idea could be that Naruto and Ichigo accidentally swap their powers. Naruto has to deal with the Soul Reaper powers in the Bleach world while Ichigo tries to handle chakra in the Naruto world. It would lead to some really funny and interesting situations as they both struggle to adapt to the new powers and the different cultures of each universe.
One idea could be that the characters from Naruto find themselves in the Bleach universe during a major Hollow attack. Naruto's skills in combat and his ability to sense negative emotions could be really useful in the fight against Hollows. For example, he could use his Shadow Clone Jutsu to confuse the Hollows while the Bleach characters use their Zanpakuto. Another plot could involve a neglected character from Naruto, like Rock Lee, being sent to the Bleach world and training with the Soul Reapers to gain new powers and prove his worth. He could learn Kidou techniques and combine them with his Taijutsu.
One idea could be a scenario where Naruto and Ichigo meet in a dimension between their worlds. They initially misunderstand each other due to their different combat styles and powers. Naruto might mistake Ichigo's Zanpakuto for a strange kunai at first. But then they realize they are both protectors of their respective realms and team up to face a common threat that is endangering both the Naruto and Bleach universes, like an ancient evil entity that feeds on spiritual and chakra energy.
One idea could be a scenario where Ichigo and Naruto meet in a strange dimension. They initially misunderstand each other but then realize they have a common goal of protecting their respective worlds. They could team up to fight a new threat that somehow has the power to destroy both the Soul Society and the Hidden Leaf Village.
Another plot could involve the Quincy from Bleach. Uryu could be mistaken for a Devil by some of the Highschool DxD characters because of his unique powers. This misunderstanding could lead to a conflict at first, but then they realize they are all on the same side against a greater threat, like a powerful fallen angel who is trying to start a war between the Hollows, Devils and Quincies.
One idea could be that the Death Eaters in the Harry Potter world somehow gain access to Hollow powers from Bleach. This could create a new kind of dark magic that the Order of the Phoenix has to deal with. Another plot could involve Hogwarts students being sent to the Soul Society for a special training exchange, and they have to adapt to the different spiritual powers and rules there. And perhaps a powerful Hollows attacks Hogwarts and the wizards have to team up with the Soul Reapers to defeat it.
A possible plot could involve the Hollows from Bleach somehow making their way into the Inuyasha universe. Inuyasha and his friends would have to team up with Ichigo and the Soul Reapers to fight them. This would create a really interesting dynamic as the different fighting styles and powers collide. The Hollows might also target the demons in Inuyasha's world, seeing them as a new source of power or prey.
Well, a cool plot could involve Ichigo somehow getting transported to Remnant. He might initially be confused but then realize he has to help the RWBY teams fight against Salem. His Hollow powers could be a great asset in battles against the Grimm. And perhaps some of the RWBY characters could gain temporary Soul Reaper powers, like Yang being able to use a zanpakuto in a really brute - force way that suits her fighting style.
A more complex plot could be centered around the concept of the Soul Society in the RWBY world. What if the RWBY characters find out about the afterlife as it exists in Bleach? They might try to find a way to communicate with their fallen comrades who are in the Soul Society. This could open up a whole new dimension of character development and exploration of themes like life, death, and the afterlife.