A plotline might involve Naruto being sent on a mission to deal with the mystery surrounding Hachishakusama. As he gets closer to her, he discovers that she has a kinder side that no one else has seen. Their relationship then develops against the backdrop of Naruto trying to convince his friends that she's not all bad. It could also be that Hachishakusama has some power that Naruto needs to save his village, and in the process of working together, love emerges.
Yes, there might be some. You can start by looking on popular fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'Naruto and Hachishakusama romance' in their search bars.
One possible plotline could be that Naruto is on a mission in the world of Fairy Tail and meets Mirajane. They start off as friends but gradually develop feelings for each other as they face challenges together. Another could be that a magical accident somehow transports Naruto to Mirajane's world and they are forced to rely on each other, leading to a romantic connection.
One possible plotline could be that Naruto somehow ends up in Starfire's universe. He meets her and is immediately intrigued by her different appearance and powers. They start off as friends but gradually develop feelings for each other as they go on adventures together and protect her planet from various threats.
Another fanfiction concept could be that Hachishakusama is somehow summoned into the Naruto world during a battle. Naruto and his friends initially think it's an enemy but then realize it's a being from another dimension. They have to figure out a way to send it back, perhaps by using some ancient sealing jutsu that Naruto has to learn specifically for this task.
A possible plotline could be that Calypso, with her alluring powers, tries to tempt Naruto away from his path of becoming Hokage. But Naruto, with his strong will, resists and instead tries to show Calypso the importance of having a noble goal. Another plotline might be that Naruto and Calypso team up to fight a powerful entity that is causing chaos in both their worlds.
One possible plotline could be Naruto using his new position as a daimyo to bring about political reform in the ninja world. He might try to end the long - standing feuds between different ninja villages by leveraging his power.
One possible plotline could be that Naruto dies during a great battle, like against Kaguya. But his spirit remains because he has some unfulfilled desires, like seeing the village fully at peace. So, as a ghost, he tries to influence the living to achieve that peace.
A possible plotline could be Orochimaru's redemption. He realizes the error of his ways and joins Naruto in protecting the ninja world. He could use his vast knowledge of jutsu and forbidden arts to help Naruto against new threats.
One plotline could be Naruto starts in his own world, discovers a portal to the Pokemon world, and decides to explore it. He might start as a novice Pokemon trainer and quickly rise in the ranks using his ninja skills.
One plotline could be that Naruto is chosen by Poseidon to be his champion in the human world. He is given special powers to protect the seas and their secrets from those who would misuse them. Naruto, with his determination, uses these new powers to fight off evil forces that are threatening the ocean's balance.