Often, other dragon slayers are paired with Ryu. They can have different fighting styles and come from different backgrounds, which makes for an interesting dynamic when they work together.
It depends on what you mean by 'famous'. If 'Ryu' is a common name in a certain community or within a specific type of media, there could be a story that is well - known among that group. For example, in the Street Fighter series, there is a character named Ryu. But if this is not related to that, it's still unclear what the 'hot ryu story' might be.
Luffy from 'One Piece' could also be an interesting crossover. Luffy's stretchy abilities combined with Ryu's martial arts would make for some unique fight scenes. They could also learn from each other's determination and loyalty to their friends.
One of the great Danmachi fanfics is 'A Different Perspective'. It offers a fresh take on the characters and their relationships within the Danmachi universe. The story delves deeper into the backstories of some minor characters and makes them more significant. Another good one is 'The Unseen Adventures'. It takes the characters on new quests that are not in the original story, adding more excitement and mystery.