One possible plot idea could be that Naruto has achieved some great power or status, and Tsunade, who is usually strong - willed, is in a situation where she has to be submissive to Naruto for the greater good of the village. For example, Naruto might have discovered a new threat and has a plan to deal with it, but Tsunade needs to follow his lead.
A plot could revolve around a training scenario. Naruto has developed a new and extremely effective training method that Tsunade wants to learn for herself or for the benefit of other shinobi. In order to learn this method, she has to submit to Naruto's teaching style. This would create a dynamic where Naruto is in control of the training process, and Tsunade has to follow his instructions, which could be a contrast to their normal relationship in the Naruto series.
One possible plot line is that Naruto is injured badly and Tsunade has to use her medical skills to save him. During his recovery, they have deep conversations about life, dreams, and the future of the village. Another could be that Tsunade decides to train Naruto in a special jutsu that only she knows, which would enhance Naruto's abilities greatly.
One possible plot could be Naruto using his charm and determination. Maybe he starts by impressing Tsunade with his growth as a ninja. He could show her his new jutsus and how far he's come in his training. Then, he gradually starts to show his affection in a more personal way, like bringing her small gifts or helping her with her Hokage duties in a very dedicated manner.
There are numerous Naruto fanfics out there. Regarding a 'Tsunade submissive a Naruto fanfic', it could be a rather unique take. It might not be as common as some other themes. Maybe you could also join Naruto fan communities on platforms like Reddit or Discord. Fans in those communities often share and discuss interesting fanfics, and someone might be able to point you in the right direction.
Another plot could involve Naruto accidentally stumbling upon Tsunade's secret past. Tsunade initially tries to keep it from him, but Naruto's determination to understand and help her makes her open up. This could then develop into a story of trust and growth for both of them.
Another plot could be that Tsunade has a long - lost relative who Naruto befriends. This relative could have a special ability that Naruto helps develop, and in the process, it brings the two families closer together. For example, the relative might have a healing ability that Naruto helps enhance with his own chakra control.
One possible plot development could be that Tsunade trains Naruto more intensively in medical ninjutsu. Since she's his grandmother, she might feel a stronger obligation to pass on her skills.
One idea could be a story where Naruto seeks Tsunade's help in mastering a new medical ninjutsu. Since Tsunade is a master in medical ninjutsu, she could take Naruto under her wing. This would not only strengthen Naruto's skills but also create a great bond between them. They could go on missions together related to healing injured ninjas in the war - torn areas.
In a Naruto and Tsunade time travel fanfic, they might travel to a time when the Uchiha clan was at its peak. Naruto could try to prevent some of the tragedies that befell the clan later. Tsunade, with her strength and wisdom, could help in diplomatic efforts. For example, she could work with the clan leaders to improve relations between the Uchiha and the rest of the village. This would not only change the future for the Uchiha but also for Naruto's own life as he has a deep connection with Sasuke, an Uchiha. And Naruto could learn new jutsu from the powerful Uchiha of that time, further enhancing his own skills.
One possible plotline could be that Tsunade and Naruto go on a dangerous mission together and Tsunade has to protect Naruto at first, but then Naruto's growth allows him to contribute significantly. Another could be that Tsunade is teaching Naruto some special medical jutsu, and they have a mentor - mentee relationship throughout the story.
A fanfic where Tsunade and Kushina train Naruto in a new and unique form of ninjutsu. They take him to a secret location and over the course of the story, Naruto masters this new skill. Along the way, they share stories and experiences, strengthening their bond as comrades and friends.