One idea could be a story where Nanao and Shunsui have to protect the family from a new and powerful Hollow threat. They work together, using their unique skills and the bond within the family to overcome the danger.
Perhaps a story where an old family secret is uncovered that puts a strain on Nanao and Shunsui's relationship. They must navigate through the lies and half - truths to preserve the family's unity and their own bond. It could involve exploring their pasts and how they came to be part of the family in the first place.
A plot could involve Nanao and Shunsui preparing a young family member for the responsibilities of being in the Soul Society. They teach about honor, duty, and the power of reiatsu in a series of training sessions and life lessons.
Have them face a difficult decision together that affects the whole family. Their different viewpoints could lead to some arguments at first, but through communication and understanding, their relationship would grow stronger. For instance, if they had to decide whether to send a family member away for training or keep them at home for safety.
One good one could be 'Shunsui and Nanao's Unspoken Bond'. It delves into their relationship in a rather sweet and somewhat flirty way. It shows how Shunsui's laid - back nature contrasts with Nanao's more serious one, creating an interesting dynamic.
Some smaller, more niche fanfiction communities or forums might also have stories about them. You can search for forums dedicated to the particular fandom they belong to. Sometimes, these smaller communities have some really unique and interesting takes on the relationship between Shunsui and Nanao.
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.
Well, for a Bleach Halibel x OC fanfiction, a plot could revolve around the OC being a time - traveler. The OC travels back in time and meets a younger Halibel before she became an Espada. This could change the course of Halibel's life and their relationship. Or, the OC could be a musician in the human world whose music can reach the spiritual realms. Halibel hears this music and is drawn to the human world to find the source, which is the OC. Also, the OC could have a special ability to communicate with water, just like Halibel has an affinity with water - based attacks. They could bond over this shared connection.
One plot idea could be that Ichigo and Eragon meet in a dimension that is a cross - between their two worlds. They have to team up to fight a common enemy that is threatening both of their universes. Their different powers, Ichigo's Soul Reaper abilities and Eragon's dragon - riding and magic, would make for an interesting combination in battles.
One idea could be that the OC is a powerful healer who joins Zaraki's squad. Their different outlooks on battle and life create an interesting dynamic. Zaraki, being all about combat strength, initially doesn't understand the value of the OC's healing abilities. But as they face tougher enemies together, he starts to see how crucial the OC is to the survival of the squad. This leads to a slow - building relationship between them.
Another plot could be that an ancient evil force targets Femichigo because she represents a new and unknown power in the Bleach universe. Ichigo vows to protect her at all costs. Along the way, they discover secrets about their connection that were hidden by the Soul Society, and they have to fight against not only the external threat but also the political intrigue within the Soul Society.
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.