One possible plotline could be that Fox Naruto has some unique powers related to his fox form that play a role in his interactions with Futa Hinata. Maybe he uses those powers to protect her in a dangerous situation.
I'm not sure about specific fanfictions with 'Fox Naruto and Futa Hinata'. You can try searching on popular fanfiction websites like FanFiction.net or Archive of Our Own. They usually have a wide variety of Naruto - related fanfictions.
One possible plotline could be that Naruto is in love with someone else entirely, like Sakura. He might be so focused on his feelings for her that he doesn't even notice Hinata's affection. For example, he could be constantly trying to impress Sakura while Hinata is left in the background, heartbroken. Another plotline could be that Naruto is so dedicated to his ninja goals and the protection of the village that he has no room in his heart for romantic love, especially not for Hinata. He could see her as just a friend and comrade, despite her deep feelings for him.
One possible plotline could be that they go on a mission to a far - off land to retrieve a powerful and ancient artifact. Along the way, Hinata's Byakugan helps them detect hidden traps and enemies. Sasuke uses his Sharingan to analyze combat situations quickly, and Naruto with his Nine - Tails chakra provides the brute strength. They face many challenges together and in the process, their teamwork and understanding of each other deepens.
One possible plotline could be that Hinata is under some sort of mind - control. Maybe an enemy uses a jutsu on her that makes her see Naruto as a threat to the village in a false way. So, she kidnaps Naruto to stop him from doing something she believes is harmful. But as the story progresses, Naruto tries to break through to her real self and free her from the mind - control.
One possible plotline could be that Naruto catches Hinata in a compromising situation that seems like cheating, but it's all a misunderstanding. Maybe she was helping a friend in secret and it looked bad. For example, she could be secretly training with another ninja to surprise Naruto with new skills, but he misinterprets it as something more inappropriate.
A plot could revolve around a dark force corrupting both Naruto and Hinata. This force might be an ancient evil that has been dormant for years. As Dark Naruto and Dark Hinata, they might target their former friends. Naruto could use his shadow clones in more menacing ways, and Hinata could use her Gentle Fist techniques to cause harm instead of protect. They could form an alliance with other outcasts or villains in the Naruto universe.
A possible plotline could be that Naruto and Hinata have a child who shows extraordinary abilities related to the Uzumaki clan. This leads to them having to protect the child from those who would want to use the child's power for evil. They seek the help of old friends and allies to keep their family safe.
Maybe they inherit some unique abilities from their Hanyou side. Naruto could gain enhanced speed and Hinata could get some sort of shadow - based power. They then use these powers to face a new, powerful enemy that the regular ninja skills of the village can't handle. This would put them in the spotlight and they would have to prove that being Hanyou is an advantage rather than a curse.
Perhaps in the fanfic, Futa is a new character in the Naruto world who has some sort of connection to Tsunade's past. Naruto gets caught in the middle of their relationship. It could involve Futa having some secrets that Tsunade is desperate to know, and Naruto helps in uncovering those secrets while also growing as a ninja himself.
Perhaps Hinata's mom is in danger due to a powerful curse placed on the Hyuga clan. Naruto, with his strong sense of justice, decides to find a way to break the curse and save her. He might go on a journey to find a sage or an ancient scroll that holds the key to lifting the curse. Along the way, he faces many challenges but his determination to save Hinata's mom drives him forward.