Both are intellectually stimulating. Hello Monster is more on the psychological side while WATCHER is heavy on the investigation. The plots are different, but the concept of people being tied together due to a past incident is strong in both; said incident lead to the decisions they made for their careers. The aspect of tension is used too, but executed differently - in Hello Monster, the tension is in characters' decisions and interactions while facing the culprit while in WATCHER it's in finding the culprit.
2 Recommended by NotMuch - Aug 13, 2019