Love and affection within the family is also a probable theme. It could be the unconditional love between siblings, or the love that extends to other family members, and how this love shapes their actions and decisions throughout the story. This can be seen in how they protect each other or care for one another in different situations.
The main character is the brother, and of course, his sister is also a central figure. Their personalities and actions drive the story forward.
Since I haven't read the 'tomodachi no imouto light novel', I can't be certain. But usually, the main character would be the one whose perspective the story is mainly told from, probably a male character if it follows the common light novel trope. And of course, the friend's sister would be a major character. There might also be other friends or family members who play important roles in the story.
One possible theme could be love and family. Since the main plot involves a marriage to Nobunaga's sister, the relationship between the protagonist and his wife, as well as their connection to Nobunaga's family, would likely be explored. Another theme might be historical adaptation. It may take historical events and figures related to Nobunaga and create a fictional story around them.
One of the main features could be the character development of the sister. Starting as a gal - like character, she may grow and change throughout the story. There could be plotlines about her making friends, dealing with school bullies or social situations due to her appearance and style. And of course, the relationship with her brother or other family members would be a central part of the story, with their interactions evolving over time.
Well, 'ore no imouto light novel' often delves into the unique bond between siblings. There could be elements of comedy as they deal with family matters, school life, and their own personal interests. It shows how they support or sometimes bicker with each other, painting a vivid picture of a family dynamic.
I'm not entirely sure about the specific plot of 'tomodachi no imouto light novel' as I haven't read it in detail. But generally, light novels often involve various themes such as friendship, relationships, and personal growth. It might be about the relationship between the main character and his friend's sister, perhaps exploring their interactions, the development of feelings, and the challenges they face in their relationship.
I'm not entirely sure specifically as I haven't read it in detail. But generally, a light novel often features a unique story with various characters and a plot that could range from adventure to slice - of - life. It might be about the relationship between characters, with 'imouto' usually referring to a younger sister in Japanese, so perhaps it has something to do with a story centered around a younger sister figure.
The 'imouto sae ireba light novel' might be centered around the concept of having a younger sister around. It could explore different aspects such as how the presence of the sister impacts the protagonist's life, the adventures they might have together, or the emotional bonds that are formed. Maybe it also has elements of Japanese culture and values embedded within the story, like family importance and loyalty, as often seen in light novels with family - related themes.
I don't know for sure as I haven't read it. But probably there is a main character who has a strong connection with his or her sister, given the title.
Another option is 'A Sister's All You Need'. It focuses on the life of a novelist and his interactions with his sister and other characters around him, sharing some of the family - centered and slice - of - life elements as 'imouto life light novel'.