One way would be if they were both transported to a different dimension. In this strange new place, they have only each other to rely on. They would need to figure out how to survive and find a way back home. This shared struggle would bring out different sides of their personalities and force them to trust each other completely, thus developing their relationship in a very distinct way.
As they get older, their relationship could potentially turn into a romantic one. Inojin might be attracted to Himawari's kind heart and strong spirit. Himawari, on the other hand, could be drawn to Inojin's creativity and determination. However, this would be a slow - developing relationship, as they would first focus on their ninja careers and protecting the village. For example, they might go on missions together and gradually realize their feelings during those dangerous and exciting times.
One possible plot could be that they are paired for a school project. As they work together closely, they start to develop feelings for each other. One day, during a moment of celebration after the successful completion of the project, they share a spontaneous kiss. It could be a sweet and innocent moment that marks the start of their relationship.
Their relationship could be developed by having them swap bodies temporarily. This would force them to understand each other on a deeper level as they experience life from the other's perspective. They would then have a newfound respect for each other.
Their relationship could be developed uniquely by having them start as enemies in a sense. For example, Sephiroth could be on a mission that Aerith unknowingly gets in the way of. But instead of killing her immediately, he's intrigued by her. This initial encounter could spark a series of events where they keep crossing paths. Each time, they learn a bit more about each other. Maybe Aerith starts to see the pain behind Sephiroth's cold exterior, and Sephiroth begins to respect Aerith's strength and determination. Over time, this could lead to a complex relationship that is part friendship, part something more, as they both struggle with their own destinies and how the other fits into it.
Their relationship could be developed uniquely by having them swap powers for a day. This would force them to understand each other on a whole new level. For instance, Draculaura would have to deal with Clawd's werewolf instincts and Clawd would have to adapt to Draculaura's vampire abilities. It would create a lot of comical and also some very heartfelt moments as they support each other through the challenges.
A unique way to develop their relationship could be through a series of challenges. For example, they are trapped in a mysterious dimension together and have to rely on each other to escape. In the process, they discover each other's strengths and weaknesses, and Kurama realizes that Kushina is not just Naruto's mother but a powerful ninja in her own right. This mutual respect and reliance would strengthen their relationship.
Another way to develop their relationship uniquely is if Aipom gets a prophecy about a great danger that Ash will face in the future. Aipom decides to secretly train itself extra hard to be able to protect Ash. When Ash finally discovers what Aipom has been doing, he is touched and their relationship becomes even stronger. This would show a different side of their relationship, with Aipom being the protector instead of the one usually being protected by Ash.
Their relationship could be developed through a shared love of transfiguration. Hermione could seek out McGonagall for extra lessons and in the process, they bond over the beauty and complexity of the subject.
Their relationship could develop uniquely if Rachel takes on a teaching role for the younger glee club members under Will's guidance. This role reversal would force them to see each other in new lights and create a deeper bond.
Maybe they enter a Ninja arts competition. Himawari, with her unique abilities, and Inojin, with his artistic ninjutsu, team up. They have to overcome rival teams who underestimate them at first. As they progress in the competition, they learn more about each other's dreams and fears, and their bond grows stronger.