Well, for starters, they could embark on an adventure to protect the Sohma family from outside threats. Naruto, with his Rasengan and other jutsu, would be a formidable protector. They might also travel to hidden ninja villages together, with Tohru learning about Naruto's world. Or perhaps they go on a quest to uncover the secrets of Tohru's mother, and along the way, they encounter all kinds of challenges, like dangerous yokai or other ninja clans who are interested in the Sohma family's unique situation.
They could go on a quest to find a powerful magical artifact. Naruto's combat skills and Lucy's knowledge of magic could be useful in navigating dangerous dungeons and fighting off enemies who also want the artifact.
Her friends could take care of her. For instance, Yuki might bring her some herbal tea that he made himself, believing it would help with her illness.
Well, their relationship could add a whole new dynamic to the plot. If Naruto is Tohru's brother, he might bring his ninja skills and sense of justice. He could protect Tohru in a more assertive way than in the original story. His presence might also attract different kinds of enemies or allies. For example, Naruto's known enemies in his own world could potentially cross over and target Tohru to get to him, creating more conflict.
They could have an adventure where they have to stop an evil wizard who is stealing chakra and magic energy. Naruto uses his ninja skills and Lucy uses her celestial spirit magic to track down the wizard and defeat him.
They could go on an adventure to find a powerful treasure that combines the power of the One Piece and some kind of ninja - related artifact. Maybe they'd have to fight against a new enemy that is a combination of pirates and rogue ninjas. They might travel to new islands where Naruto's ninjutsu would be useful for exploring hidden caves, and Luffy's stretching ability would help them reach high places or cross large gaps.
They might have adventures where Naruto's brotherly instincts lead the way. Maybe they go on a mission to protect a village that has a special meaning to Naruto as a 'brother' figure to Team 7. He would be extra determined to keep it safe.
Maybe they embark on an adventure to help a small, oppressed village. They use their combined skills to overthrow the tyrant ruling the village and then stay for a while to help rebuild it. During this time, they learn about different ways of life and make new friends. This adventure would strengthen their bond and also their reputations as great shinobi.
Typically, in tohru and akito lemon fanfiction, Tohru may exhibit a side of her that is more in touch with her own desires and feelings towards Akito. Akito might be depicted as being more open to change and growth in relation to Tohru. These characteristics are often used to drive the relationship forward in a more romantic or passionate way, but again, this can vary greatly from one fanfiction to another. It's also important to remember that fanfiction is a form of creative interpretation, and not all portrayals will be the same as the original source material.
They could have adventures where they explore different dimensions. Naruto's ability to travel through his world could be combined with Ben's inter - galactic travels using the Omnitrix. They might end up in a dimension full of strange creatures and have to fight their way out together.
They might go on a mission to find a rare herb in a dangerous forest. Naruto's determination and Anko's knowledge of the area could lead them to the herb and also encounter some interesting creatures along the way.