Fanfiction.net might also be a place to look. However, the content there can be a bit more hit - or - miss. You'll need to search specifically for Pokemon Sun and Moon yaoi. Maybe also check out some Pokemon - centric fan forums where people might share their own works or recommend good yaoi fanfictions.
Another option could be Tumblr. There are many fan communities on Tumblr that are into Pokemon. Some users create and share yaoi fanfictions about Pokemon Sun and Moon. You can search through relevant tags to find what you're looking for, but be aware that the quality can vary widely.
One popular theme is the relationship between the trainers. For example, the relationship between the main character and a rival trainer can be explored in a yaoi context. Another theme could be the Pokemon themselves being involved in some way, like having a special bond with the characters that influences the yaoi relationship.
A good Greninja fanfiction in the Pokemon Sun and Moon universe often has well - developed characters. Greninja itself should have a distinct personality, not just be a copy of what we see in the games. The author should give it more depth, like its thoughts, feelings, and relationships with other characters.
In Pokemon Sun and Moon fanfiction, Gladion is a character that can bring a lot of depth to a story. His internal struggles, such as his conflict between his own goals and the expectations of those around him, are often explored. His growth as a character is also a popular aspect. Writers might show how he overcomes his insecurities and becomes a stronger trainer and person. His Pokemon battles in fanfictions are usually intense, as his Pokemon are not only strong but also have a special bond with him.
One possible fanfiction could be about Wicke's backstory. Maybe she has a hidden past as a trainer herself before devoting her life to research in Alola. In the fanfiction, she could discover an ancient Pokemon that has a connection to the history of the Alola region and she has to protect it from Team Skull.
Lana's fanfiction is appealing because it allows fans to see her in different situations. Maybe she goes on a journey outside of Alola and has to adapt to new environments. This shows her versatility as a character.
Gladion's role in Pokemon Sun and Moon fanfiction can be multi - faceted. He can be a rival to the protagonist, pushing them to become better trainers. His connection to Team Skull also adds an interesting layer to the story. Moreover, his relationship with other characters like the Kahunas can be explored in fanfiction, creating more complex storylines.
One possible fanfiction could be about Mallow's journey to discover new and rare ingredients for her cooking. Maybe she ventures into a mysterious forest in Alola and meets a Pokemon that has the ability to guide her to a hidden grove filled with unique berries and herbs that she can use to create a special dish for a big island festival.
In some fanfictions, Lillie is often portrayed as a more delicate and reserved character. Moon, on the other hand, is seen as the bolder one. For example, when they enter a new area full of unknown Pokemon, Moon might be the first to approach and try to interact, while Lillie hangs back a bit.
One possible fanfiction could be about Sun and Lillie going on an adventure together in the Alola region. They might discover a new and rare Pokemon that only appears during a certain lunar phase. Sun could use his skills as a trainer to protect Lillie from any potential danger, and in the process, their relationship could grow deeper.
I'm not sure about a specific one off the top of my head, but you can check out fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'Lillie Pokemon Sun and Moon' and you'll likely find a bunch of options. Look for ones with high ratings and a lot of reviews.