Healer

University student, Takatsuki Minato, likes things to be clean and in order while her stepbrother, Takatsuki Toru, is a bit of a player. One day, while cosplaying as a high-school student in a fashionable district in Tokyo, Minato accidentally bumps into Toru and quickly lies about her identity. To her surprise, Toru appears to take an interest in her alternate identity, Mina, and asks her out. Thinking that she might be able to cure Toru out of his playboy ways, Minato continues to disguise herself as Mina but will she be able to keep up the charade when she starts developing feelings for Toru?

Both dramas ML are best agents in their fields
He lost someone close to him
Related to whole mystery and conspiracy
both include a lot of action, crimes and investigations

ML is superman archetype, loner,
FL curious and brave despite childhood trauma
Both support justice in their own way , ML seemingly hesitant to get involved in worldly affairs
Dark but witty dialogue to create balance
Intriguing investigative adventure with romance at its core
****Please note these parallels are made after only two episodes -rest of episodes may alter this opinion.

If you like thriller, mystery & investigative story, Healer has it too. It's just balanced with comedy, romance & action. I noticed that the (old)... music used in ep1 in Signal was also used in Healer on their flashback scenes....
Music is added to have more thrilling feels....

- The ML of Cambrian Period works as a masked killer under his adopted father who is the leader of a criminal gang. You would never expect an innocent, puppy like, pretty boy behind the mask.
- Both have action, crime, mystery, romance