I have not watched much horror because I tend to avoid those and watch romantic comedies instead. Therefore, I am not well versed in the horror genre. What I can tell, the characters in the japanese Pulse or Kairo and the American Pulse are involved in a regular life that is interrupted by a terrible event that is happening around them. Their use of music, lighting, and editing is all different for two different effects.
In the Japanese film, the horror was very subtle. You leave the movie feeling terribly creeped out, although you never have the feeling of having jumped in your seat. The music was mostly quiet, and silence was used very strategically for an even creepier effect. The lighting was bright and natural when the characters were outside, which conveyed a sense of normal life. While the characters began to see things occurring, the lighting would change to dark and it was flexible based on the moods. The framing and editing was not so quick, with most of the shots being quite wide so you can see the dark shadow creepily behind the character. The acting was also subtle for the more mentally testing film.
In the American film, the music was very loud and cued emotions during the events that were occurring. The horror was in your face, and it was meant to make you jump in your seat. The lighting was super dark and had very high contrast the whole movie, event during the day. The editing was very close, so it made the movie viewer much more involved in the story. The acting was much more emotional, and the themes were drawn out to be more exaggerated compared to the Japanese film.
Overall, the horror in these two films are very different. The genre includes the establishing characters and an event changes their lives. In Kairo, nothing could be done but to run away from the event. In Pulse, they could upload the virus that would shut down the system and save the world. Watching these two movies confused me when pinpointing horror as a first time watcher for sure.