Well, a lot of khr oc x all yaoi fanfictions play with different tropes. Some might have the oc as a sort of catalyst for the relationships between the other characters. They can bring out new sides of the characters, and in a yaoi context, it can lead to some really engaging and heart - warming or even heart - wrenching stories. The best ones are those that are able to balance the oc's own story with the yaoi relationships.
There are some khr oc x all yaoi fanfictions that are known for their interesting plot twists. Maybe the oc is from a different world and has to adapt to the relationships in the khr universe while also getting involved in yaoi - themed romances. It's really exciting to see how the author unfolds such a complex setup.
One great khr oc x all yaoi fanfiction could be those that focus on character development. For example, a story where the original character (oc) has to navigate through complex relationships with all the characters in a unique way. The charm often lies in how the oc interacts with different personalities in the yaoi context.