One possible scenario could be that Oga and Aoi's kiss was a moment of sudden realization of their feelings for each other. Maybe they were in a beautiful garden, surrounded by blooming flowers. The sun was setting, casting a warm glow. Oga, who had been secretly in love with Aoi for a long time, finally mustered the courage to lean in and kiss her. Aoi, initially surprised, then melted into the kiss, feeling all the unspoken emotions between them.
One common theme is friendship. Yusaku's relationships with other characters are often explored in fanfics, showing how he bonds with different people.
Well, it's not ethical at all. Fanfiction should generally stay within the boundaries of respect for the source material. When it comes to creating erotic content related to a character, it not only violates the moral code but can also be offensive to the fans who love the character for its original qualities and the story it belongs to. It can also potentially cause issues with the copyright holders of the original work.
Well, in the manga, Aoi Tsubaki and Odanna do get married. It's a significant plot point that brings their story to a happy conclusion. The build-up to their marriage is filled with various challenges and sweet moments.