One common theme could be the exploration of their relationship dynamics. It might involve how they interact, whether it's in a friendly way or with some underlying tension.
The Beginning After the End manga has indeed finished. It provided a satisfying conclusion to the characters' arcs and the overall narrative. Maybe there'll be spin-offs or related projects in the future, but for now, the main story is complete.
One common theme could be the exploration of complex relationships. Since yaoi often involves male - male relationships, there might be a focus on the emotional connection and the power dynamics between 'greed ler' and 'once ler'.