One plot idea could be that Keita and Riko are in a band together. They start off as just bandmates, but as they go through the ups and downs of the music industry, they develop a deep friendship and then eventually fall in love. Their journey could involve dealing with record labels, jealous bandmates, and the pressure to succeed.
Typical themes might include the relationship development between Riko and Keita. It could involve their daily interactions, how they handle the unique situation of their relationship in the context of the 'kiss x sis' story.
There might be a lot of such fanfictions out there. However, without delving deep into that particular fandom myself, it's hard to point out exact ones. You could also check out relevant fan communities on social media platforms where fans might share their favorite fanfictions about Riko and Keita from 'kiss x sis'.
They could participate in a school competition together, like a sports event or a talent show. Keita and Riko would practice a lot, and during this time, they would have many sweet and funny moments. There could be some friendly rivalry with other students too. And as they strive for victory, their relationship could develop further, with Riko cheering Keita on in a really enthusiastic way and Keita being inspired by her support.
In writing Keita's character development, explore his friendships outside of his relationship with Riko. How do his interactions with other friends influence his views on his relationship with Riko? Maybe he starts to see the uniqueness of their bond more clearly. For Riko, develop her character by showing how she copes with jealousy. Instead of just being a jealous character all the time, she could learn to trust Keita more. This change in her behavior would be a significant part of her character development, and it would also impact the overall relationship dynamic in the fanfiction.
I'm not very familiar with this specific 'kiss x sis keita x ako fanfic'. But generally, a fanfic like this might explore the relationships and interactions between the characters Keita and Ako from 'kiss x sis'. It could be about their growth, emotional bonds, or adventures within the context of the story's setting.
One great fanfic could be 'Reg and Riko's Adventure Beyond'. It beautifully captures their relationship as they explore deeper into the Abyss. The author does an amazing job of showing Reg's protective nature towards Riko.
Some smaller, more niche fanfic communities or forums dedicated to the source material of Kanna and Riko might also have unique 'kanna x riko fanfic'. You can search for these by looking for forums related to the series that these characters are from. However, make sure to follow the rules of these communities when looking for fanfics.
One great 'kanna x riko fanfic' could be 'Adventures of Kanna and Riko' which focuses on their friendship growing as they explore a magical world together. It has a really engaging plot and well - developed characters.