As I have no knowledge of 'little sister a novel', it's impossible for me to describe its plot. You might consider reaching out to book clubs or groups dedicated to reading and discussing novels. They may have members who are familiar with this book and can share insights about its plot.
Maybe it could be about a little sister who accidentally shrinks due to a magical spell. Then she has to face all kinds of challenges in a world that has suddenly become huge for her, like trying to get back to her normal size while avoiding being stepped on by the family cat.
Perhaps in a shrinking little sister story, there's some sort of scientific experiment gone wrong in the house. The little sister is caught in the blast and shrinks. She has to communicate with her family in creative ways since they can't immediately see her. She might use her wits to get their attention, like making tiny fires to create smoke signals. In the end, her older brother, who is a science whiz, figures out how to reverse the process.
Maybe the sexy little sister is an artist. She creates beautiful paintings that are full of life and passion. One day, a famous art collector comes to town and stumbles upon her work in a small gallery. He is so impressed by her talent and the way she expresses herself through her art that he decides to sponsor her to have her own solo exhibition in a major city, which launches her art career.
One plot could be centered around a family secret. The big sister discovers that she is part of a long line of women who can grow to a giant size. She has to keep it a secret from everyone, including the little sister. However, one day the little sister accidentally finds out. At first, she is scared, but the big sister explains everything. Together, they use the big sister's ability to help their community, like saving it from a flood by building huge dams in her giant form.
Well, one possible plot could be that the little sister discovers a magical item that makes her grow into a giantess. At first, she's scared and confused, but then she realizes she can use her new size to protect her family and the town from a big threat, like a huge monster. She uses her strength and size to fight the monster and becomes a hero in the end.
Well, it could be about the main character having a really crazy day babysitting their little sister. Maybe the sister gets into all kinds of mischief like painting on the walls or trying to feed the dog chocolate. And the babysitter has to figure out how to deal with it all while also trying to have some fun with her.
A sweet little sister could start a small garden in her backyard. She plants different kinds of flowers and vegetables. As she takes care of the garden, she discovers that there are some little bugs that are also living there. Instead of getting rid of them, she learns about how they are important for the ecosystem of the garden. She then shares her knowledge about the garden and the bugs with her friends and neighbors, spreading her love for nature.
The plot could be that in a family business, the little sister, seeing the business in trouble, takes control. She might come up with new marketing ideas, like using social media in a different way to attract more customers. For example, she could start a viral campaign that features the family's products in an interesting and unique way.
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.
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.