One idea could be that they meet in a dangerous situation. For example, they are in the middle of a pirate attack on a town. Smoker, being a Marine, is focused on stopping the pirates while Hina, also a Marine, has her own approach. Their different methods might initially cause some friction but later lead to respect and a budding relationship as they work together to protect the town.
For Smoker, you can show his growth in terms of his leadership skills. Maybe at the start of the fanfic, he is a bit too head - strong. But as he works with Hina, he learns to be more diplomatic. For Hina, her character can be developed by showing her softer side. Usually she is seen as strict, but in the fanfic, she could show kindness towards Smoker which is a new side of her.
A great plot could be that the OC is a doctor with a mysterious past. Hina gets injured during a battle and the OC is the only one who can save her. As the OC nurses Hina back to health, they start to have long conversations. The OC tells Hina about different cultures and places in the One Piece world that she has never heard of. This makes Hina see the world in a new light, and she starts to fall for the OC's knowledge and kind heart.
One possible plot could be that the OC is a new pirate in the One Piece world and meets Hina during an island stop. They start off as rivals, constantly trying to outdo each other in various tasks like treasure hunting or helping the local villagers. But as time goes on, they realize they have more in common than they thought and develop a deep friendship that could potentially turn into something more.
One idea could be a story where JB and Yugyeom are on a journey to discover a long - lost musical treasure. They face various challenges along the way, like dealing with rival musicians who also want the treasure. Their friendship grows stronger as they overcome each obstacle.
One plot could be that Stitch and Angel are on an adventure together to save their friends from a new threat on their island. They have to use their unique abilities, like Stitch's super strength and Angel's singing powers, to overcome obstacles.
In the fanfic, Freddie could be an artist who is inspired by a stray cat he often sees. He starts to draw the cat in different scenarios and situations. As he does this, he feels a connection with the cat as if it's guiding his artistic vision. Eventually, they meet in a really unexpected way and their relationship blossoms from there.
A possible plot could be that Margaret gets into trouble with a powerful pirate group. Luffy comes to her rescue and then they decide to travel together for a while. During this time, Margaret learns about Luffy's dreams and they support each other in achieving their individual goals. They might also encounter some strange islands and have to work together to survive on them.
Maybe Grayfia is on a mission in the Naruto world. She has to team up with Naruto to fight a common enemy. During their time together, they learn about each other's pasts and dreams. Naruto's never - give - up attitude impresses Grayfia, and her elegance and power intrigue Naruto. This could lead to a romantic relationship developing between them.
One plot idea could be that Naruto somehow ends up in Grayfia's world and they have to team up to face a common threat. Maybe a powerful dark force is endangering both their realms.
One idea could be that they team up for a virtual adventure in a fantasy game world. They might face various challenges together and develop a strong friendship or even a romantic relationship along the way.