Well, a smut novel refers to a book where the focus is heavily on sexual themes and often has very detailed and graphic descriptions of sexual acts. It's not for everyone and is usually considered more adult-oriented.
Here is a threesome story. There were three friends, Tom, Jerry and Lily. One day, they decided to go on a hiking adventure. They climbed up the mountain together. Along the way, Tom was good at finding the path, Jerry was responsible for carrying the food and water, and Lily cheered them up with her jokes. When they reached the top, they watched the beautiful sunset together, sharing this wonderful moment as a threesome of good friends.
No, in most cases, 'threesome fanfic' is not appropriate. It often involves themes that are not suitable for general audiences, especially those that are underage or who do not wish to be exposed to such sexual or adult - like content.
A 'threesome fanfic' is a type of fan - created fictional work that often involves a romantic or sexual scenario among three characters. However, this type of content may not be suitable for all audiences and often goes against the ethical guidelines of many platforms.
One character could be Nora. Nora is energetic and fun - loving, just like Ruby in some ways. Their combined energy could make for a very lively threesome scenario in fanfiction. Ren might also be a candidate. Ren's calm and collected nature would contrast well with Ruby's more exuberant personality. Together with another character, perhaps Weiss, they could form an interesting threesome. Also, Emerald could be in a threesome with Ruby. Emerald has her own motives and a somewhat complex personality. Her interactions with Ruby, especially in a threesome situation, could add a lot of depth to the fanfiction.