One possible plot could be that Naruto's little sister is also a ninja in training. She might struggle with the same kind of ostracism Naruto faced because of the Nine - Tails inside him. However, she could also be a source of great support for Naruto, helping him through his toughest times and together they could train to become stronger. Maybe she has a unique ninja ability that even Naruto is in awe of.
Well, perhaps in the fanfiction, Naruto's little sister was separated from him at a young age. She could be raised in a different village. As she grows up, she discovers her relation to Naruto. She then decides to journey to Konoha to find him. Along the way, she has to face many challenges and enemies. When she finally meets Naruto, they have to deal with the fact that they are siblings but also have different loyalties to their respective villages.
Often, there is a part where Naruto has to prove himself to his sister or gain her trust. Since she may not know him well or may be scared at first. Also, Naruto usually has to overcome his own limitations in power to be able to protect her effectively. For example, he might have to learn a new jutsu or master an existing one in a short time. And there is always the emotional aspect of the bond between them growing stronger as he protects her from different perils.
One possible plot could be that the little sister has a special power. For Naruto, she might be a ninja with unique jutsu. In the Sekirei world, she could be a Sekirei with a new type of ability. Maybe she gets caught in the middle of a conflict between the two worlds, and Naruto and the Sekirei have to work together to protect her.
In this fanfiction, Lemon could be a very curious and adventurous character. She hears stories about Naruto's heroic deeds and wants to be just like him. So, she secretly follows Naruto on one of his missions. Naruto is initially angry but then realizes that she has potential. He starts training her on the mission, and together they face a powerful enemy. Through this experience, their relationship as siblings becomes stronger.
In this fanfiction, Naruto's ninja skills could play a role in his sister's protection. He might teach her basic self - defense moves early on. Also, his friends in the village could become like aunts and uncles to his sister, providing different kinds of support and influence. For instance, Sakura could teach her some medical knowledge.
One idea could be that the little human sister discovers the Tmnt's lair by accident. Maybe she was exploring the sewers for a school project on urban infrastructure. Once there, she befriends the turtles and helps them out with some human - world tasks like getting supplies or finding information on their latest enemy.
The 'naruto sealed in his sister fanfiction' might explore the relationship between Naruto and his sister in a very unique way. If Naruto is sealed in her, they might be able to communicate in some mental way. His sister could struggle with the sudden change in her body, having Naruto's essence within her. There could be a plot where she has to figure out how to release Naruto without causing harm to either of them, and in the process, they both grow stronger and closer as siblings while also facing off against various antagonists who are after Naruto's power that is now 'housed' within his sister.
Well, it could be about Kurenai having some secret connection to Naruto as his sister. Maybe she discovers this truth and has to deal with the implications. For example, she might have to protect Naruto from new threats while also coming to terms with her new - found family relation.
There could be a fanfiction where Naruto's little sister is sent on a special mission. She has to go undercover in an enemy village. Along the way, she makes new friends who are initially suspicious of her but come to respect her as they see her determination and kind heart. She also uncovers a plot that could endanger both her village and the one she's infiltrated.
Family bonds are a very common theme. It explores how Naruto and his little sister rely on each other, love each other unconditionally, and how their family connection is a source of strength. For example, in many fanfics, they might fight to protect each other from the threats in the ninja world.
Sakura could be a great character to include. She could act as a mentor to Naruto's little sister, teaching her about medical ninjutsu. Another good character would be Kakashi. He could train her in combat and stealth skills. And of course, Naruto himself should be in it, as their relationship would be a central part of the story.