The idea of adventure and exploration in the Alola region, which is the setting of Pokemon Sun and Moon, is often used. The two characters in the yaoi relationship might go on adventures together, facing challenges and growing closer through those experiences. There's also the theme of self - discovery. The characters might discover new things about themselves and their feelings during their journey in the Alola region.
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.
One popular theme is Lillie's growth. In many fanfics, she starts as a somewhat shy and reserved character. Her journey in Pokemon Sun and Moon is about finding her own strength. Another theme could be her relationship with the protagonist. It often explores how they support each other through their adventures. And of course, the theme of Pokemon battles and training also plays a role as it's set in the Pokemon universe.
One popular theme is adventure. Ash and Lillie might go on various quests together in the Alola region, exploring new places and encountering different Pokemon. Another theme is friendship. Their relationship could develop from just being acquaintances to really close friends who support each other through thick and thin. Also, growth is a common theme. Lillie might overcome her shyness and fear of Pokemon with Ash's help, while Ash could grow in his understanding of different cultures in Alola through his interactions with Lillie.
One common theme could be the relationship between the main character and a rival in a more romantic or emotional context. For example, the dynamic between Gold and Silver characters might be explored in terms of unspoken feelings and hidden desires. Another theme could be how they support each other during their Pokemon - collecting adventures in a yaoi - inspired way. It could also be about their growth together, not just as Pokemon trainers but as individuals in a relationship.
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.
One common plotline is Ash's various female companions in the Pokemon Sun and Moon series forming a closer bond with him, like Lillie gradually opening up more to Ash and having adventures that bring them closer. Another could be Mallow cooking special meals for Ash, which is seen as a form of her showing her affection in the fanfiction world. Also, the idea of them all traveling together and facing challenges as a group, with Ash at the center of their little 'harem' is quite popular.
Lillie is often a popular character. Her kind nature and her growth throughout the story can be really interesting to explore in fanfiction.
The trial captains are quite popular in Pokemon Sun and Moon slash fanfiction. For example, Kiawe might be depicted in various new situations. Writers could show him having to deal with a new type of Pokemon problem or having an unexpected friendship with another character. Gladion is also popular as he has a mysterious aura, and fanfictions often delve into his past and his true motives.
Lillie is often a popular character. She has an interesting backstory and her relationship with the Pokemon is quite endearing. Another popular one is Ash. He is a well - known character from the Pokemon series and his adventures in the Alola region in Pokemon Sun and Moon are always exciting to read about in fanfiction. And of course, Team Skull members can be popular too, as they add a bit of a 'bad boy' element to the stories.
One possible theme could be friendship. Lillie's return might reaffirm the importance of the friendships she had before she left. Another theme could be growth. Maybe she has grown in some way during her absence and her return shows this development.
A common theme is the power of unity. The Ultra Guardians often work together in the original concept, and this is emphasized in fanfiction. They rely on each other's skills and Pokemon to overcome challenges. For instance, when facing a powerful Legendary Pokemon, they combine their efforts and strategies.