Perhaps a fanfic where Risa is a new transfer student and Sirzech is assigned to show her around. Along the way, they get involved in a mystery involving missing students. Their relationship could grow as they work to solve this mystery, with Sirzech protecting Risa at times and Risa using her wits to help Sirzech in making crucial decisions.
Well, without further details, it's hard to say a great deal. But generally, a teacher like Risa Onodera could be involved in curriculum planning, student assessment, and providing guidance to her students. She may also participate in school activities and collaborate with other teachers for the betterment of the educational environment.
Well, in addition to Otani and Risa, their baby could also be considered a main character in a sense. After all, the whole story revolves around the new addition to their family. The baby's presence affects their relationship, their daily lives, and the way they interact with the world around them. So, even though it's a new life and can't really act like a typical main character at first, it still has a major impact on the story.
If we assume that 'satoshi and risa' have some distinct characteristics in their relationship in the original source material, then a lemon fanfic about them might be unique in how it explores their more intimate or passionate side. But without knowing the exact nature of these characters, it's just speculation.
Common themes could include friendship. Since they are two characters, their relationship might be explored in terms of how they support and understand each other as friends.
Well, there's a fanfiction where Risa is a trainer who stumbles upon a rare Mew. This Mew has some special abilities that are different from the norm. As the story progresses, Risa and Mew form an unbreakable bond and face off against powerful foes together. Also, there could be a fanfiction that focuses on Risa's attempts to understand Mew's language and the hilarity and heartwarming moments that come from their miscommunications at first.
One interesting Pokemon Ash and Risa fanfiction could be where they team up to explore a new, uncharted region in the Pokemon world. They might encounter rare and powerful Pokemon that no one has ever seen before. In this fanfiction, their friendship could grow as they face challenges together and learn new battle strategies.
Perhaps a plot where their baby has some unique trait or ability that surprises them. It could be something like the baby being extremely perceptive at a very young age, and they have to learn how to parent in this new situation. For example, the baby seems to understand their emotions and tries to comfort them when they're sad, which makes Otani and Risa reevaluate their own relationship and how they want to raise their child.
You can try fanfic websites like Archive of Our Own (AO3). It has a large collection of fanfics from various fandoms, including otani x risa. Just search for the relevant tags and you should be able to find some great ones.