It's action, and the production-level is high quality. The two also has plot that are not main character-driven, meaning that it does not heavily depend on the progress of the romantic relationship between the two leads. The parallel of the two main leads of the two series are also uncanny.

The main leads are polar opposites. Both main leads in "Killer and Healer" and "The Sign" have opposite personalities that complement each other well.

- main leads are related to the mythical creature naga (one is naga, the BL one is reincarnation of naga)
- characters are related to mythical beings of naga and garuda
- main leads didn't remember their past lives in the beginning of the series
- third-wheel from the past

- main characters are in the police force
- "hot" and "cool" main leads that complement each other
- mystery cases