To give a summary of the plot of Nijigahara Holograph would be an impossible feat, maybe even for the mangaka, Asano Inio (known for several works including Oyasumi Punpun). The story of this manga often flips between a 10 year time gap sometimes making it a little difficult to follow. It centers around a group of people in a rural area of Japan. A swarm of butterflies as well as extreme heat has caused problems for some people while others see a slightly different meaning to the butterflies that seem to glow even at night. 10 years in the past, it centers around a fifth grade class, their families, and teachers. In both times, murder, sex, violence, depression, and boredom are abound. The story hides many facts from the reader and slowly pieces together the connections between people, who people really are and their pasts, and gradually builds a dark, psychological tale that questions why God would even make humans the way they are.
The art helps accentuate the psychological aspects of the manga. Often panels will be just black backgrounds with white writing which I think helps establish a sense of separation and loneliness for whoever's thoughts the words belong to. The characters are drawn very well, but the author often chooses to display them in an ugly way. The author focuses on the negative aspects of humanity from lust to greed to despair and uses the art to perfectly follow the emotions and feelings being displayed.
This is actually a heavily character driven story. The interactions between the characters and with themselves are given top priority and slowly broadened as the story progresses. The characters mostly remain a mystery even at the end. There are many great twists involving the characters and their relationships, and I never saw any of them coming ahead of time. There is no one main character and instead the author switches around between characters in order to put the pieces of the story together. Suzuzki, a boy who tried to commit suicide at his old school but failed and now intentionally separates himself from others, and Komatsuzaki, a bully who drastically changes his personality after taking crossing the line with his friends, are two of the most important ones. The story tends to be split between the two of them and all of the other characters connect to one or both of them.
This is a great psychological manga which I highly recommend as long as you don't mind depressing or open-ended stories. It's difficult to really understand it as a whole, but that's not what the story was trying to do anyway. It really makes you question humanity, God, and why God would make humans the way they are.
