Happiness

Happiness (: 행복, : Haengbog) is a South Korean psychological thriller series.

The the first series focuses on a few officers and detectives in the  cities of, , and , who are investigating series of strange murders, with the case soon growing into an investigation of a terrorist cult, which plans to take advantage of the current instability in the country in order to get power.

Premise
, Min Kwang-su, has gotten into a major corruption-related scandal, prompting Koreans to organize protest movements, calling for his resignation.

In the meanwhile, however, police in is investigating four similar murders, which are reminiscent of sacrifices, with officers soon seeing strange figures watching them and their families, noticing a sudden spike in drug overdose cases, and are alarmed when they hear of similar murders in other cities as well, leading them to look wider.

The second season also includes the soldiers from the, as well as experts from the , who are trying to stop an outbreak of the , which spread onto the population after a bioterrorist attack from the cult.

Development
The writer of the series has noted that the idea came to him from a post on r/somnivexillology, a subreddit used to post flags people have seen in their dreams.

One of such posts, made by user DMNOFCAN, told about the "happy" cult, which took over Korea after a civil war. The idea got some minor following among the users, and eventually a separate subreddit, r/happyearth.

Music
According to the composer, the soundtrack was largely inspired by Kikiyama's soundtrack for, as well as Christian Salyer's soundtrack for , and music of Norwegian ambient artist. It has been noticed by critics, who remarked that it was "chilling" and "eerie" and was "perfect for the show".