In some fanfictions, Naruto might use a powerful jutsu. Maybe he discovers an ancient sealing technique that can bring back the dead for a short time. He could also have found some rare chakra-infused artifact that has the power to revive the First Hokage.
The cells can also introduce internal conflicts. A character might struggle with the foreign power within them. They could be afraid of losing control, like Orochimaru was with his various experiments. This internal struggle is a great way to develop the character's emotional side and show their insecurities.
To develop Hashirama's ghost, we could give him a sense of purpose. He could be a protector of the village in the afterlife. So, when he senses a great danger approaching the village, he decides to reach out to Naruto. He could have a deep connection to the natural world even as a ghost, and his powers could be related to manipulating nature spirits. He could teach Naruto how to communicate with these spirits and gain their assistance in times of need.
Well, it could be that Naruto discovers an ancient artifact that contains Hashirama's chakra. When he touches it or unlocks its power in some way, the chakra gets transferred to him. For example, the artifact might be hidden in a secret location and Naruto stumbles upon it during one of his adventures.
Naruto's positive attitude and his belief in friendship might make Hashirama more open - minded. For example, if Hashirama was hesitant about an alliance, Naruto could convince him with his own experiences of forming bonds across clans.
When writing, think about the historical context of their world. The feudal - like setting with clans and power struggles can add depth to the romance. You can have Madara as a rival in love, but also show his vulnerable side. Maybe he's in love with Mito because she's the only one who seems to understand his dark thoughts. For Hashirama, his love for Mito could be pure and simple, like a light in the chaos of their world.
First, research about Hashirama thoroughly. Know his personality, his abilities, and his relationships. Then, come up with a unique plot. For example, you could focus on his friendship with Madara in a different light. Also, make your characters' dialogues realistic.
Hashirama's revival might also bring back old wisdom and knowledge. He could teach the new generation of shinobi things that have been lost over time. However, there could also be political issues. Some might not be happy with a long - dead Hokage coming back and potentially interfering in current affairs. And his revival could also have an impact on Naruto's own growth. With Hashirama around, Naruto might have to re - evaluate his role as a leader and a shinobi.
The relationship can start with Naruto being in awe of Hashirama as a great founder. Then, Hashirama could notice Naruto's strong will. They could start with simple conversations about the village's future.
First, you need to come up with a concept. It could be based on their similarities or differences. For example, their strong will to protect the village. Then, create an outline that includes the beginning, middle, and end of the story.