Nagi is the only child of a famous writer. Not only was her father famous, but Kirima Seiichi was fairly prolific, averaging one book a month and usually at least ten books a year. This man originally started writing novels; however, he is better known for all of his work except those. Even his biggest fans reported never touching his novels. His writing also seemed powerful enough that Seiichi called himself an "enemy of society" - not because he deliberately sought to unhinge things on a greater scale in the world, mind you. No. It was merely that he noticed a lot of his fans seemed to be people who might be further along the evolutionary path, and they kept dying or going missing. Sooner or later "they" would come for him, a dangerous "modern day enlightenment thinker." And they did.
When he wasn't writing novels, the base of his works was comprised of dissertative essays, summaries, commentaries, and books on topics such as criminal psychology/depth psychology, history, and classic literature. Eventually he stopped writing novels and concentrated on what sold. His fans never seemed to notice the difference. The base of his works were written during the 1980s and maybe early 1990s in Boogiepop-verse, where he probably was assassinated in... 1990 or 1991. (I cannot be sure, and am judging this off of Nagi being 17 or 18 when the first light novel came out, whereas her father died when she was ten. The timeline is a little unclear so this is the best I can do.)
As for the writing style, ambiguity was a distinct characteristic. Nagi herself has always wondered why his books sold so well. The translation notes for the first light novel state the following: "Seiichi's quotes are always a bit of a nightmare to translate, as they have to strike a balance between seeming cryptic but being vaguely understandable. Our translation is the result of studying the Japanese closely and puzzling out the meaning of the passages before ever translating a word" (p. 233). In Boogiepop at Dawn, Dr. Kisugi's opinion of the man's works seems to be that the writing itself was fairly slapdash as far as works in the psychological field go, but that he had a terrible habit of hitting the nail on the head due to pure instinct. In Boogiepop Returns: VS Imaginator Part Two, Asukai Jin notes Seiichi's twisted grammar and cannot decide if the writer is optimistic or resigned.
Below is a listing of all the Kirima Seiichi book titles and quotes I've been able to locate in the light novels and the anime. Since most of the light novels have not been translated into English even by fans, it's obviously not exhaustive.
- The Victor's Principle: The Victim's Future
- The Scream Inside-Multiple Personality Disorder
- When a Man Kills a Man
- Where the Killer's Mind Changes
- A Nightmare of Boredom
- The Proliferation of 'Dunno'
- VS Imaginator
- Isolation and Faith
- "The past will often attack the present with the pain of your memories." - source unknown (Boogiepop Phantom episode 6)
- "The brain is a microcosm creating its own stories. People then live out these stories." - source unknown (Boogiepop Phantom episode 8)
- "Time does not exist. Only the illusion of memories exists." - source unknown (Boogiepop Phantom episode 8)
- "Existence does not rely on matter. Everything is phantom." - source unknown (Boogiepop Phantom episode 8)
- "The waking dream called the world is constantly changing. What's so sad about that?" - source unknown (Boogiepop Phantom episode 8)
- "Pure perfection has no past. That's how you live purely." - source unknown (Boogiepop Phantom episode 8)
- How can you say you are a phantom?" - source unknown (Boogiepop Phantom episode 8)
- "The human psyche is open to the possibilities of both good and evil. In my opinion, multiple personality disorder occurs when one of these possibilities, suppressed by societal pressures, declares independence and fights to exist. Regardless of how diseased the result or how destructive it is on the host body and those around it, the possibility makes no distinction between good and evil." - The Scream Inside-Multiple Personality Disorder (Boogiepop & Others Chapter 1)
- "Possibility, or what we refer to as Imagination, is 99% imitation. The real deal is only 1%. The problem is, this 1% is simultaneously referred to as Evil." - VS Imaginator (Boogiepop Returns: VS Imaginator Part One Prelude)
- "If you wish to be good, then do not have dealings with the future. In most cases, that only leads to distortion." - VS Imaginator (Boogiepop Returns: VS Imaginator Part One Chapter One)
- "You can fall in love if you like. All I can do...is pray it does not destroy you both." - VS Imaginator (Boogiepop Returns: VS Imaginator Part One Chapter Two)
- "Do not doubt your work. No matter how pointless or unrewarding it may appear to be, anything is better than knowing for certain that it actually is." - VS Imaginator (Boogiepop Returns: VS Imaginator Part One Chapter Three)
- "Why are we afraid of the dark? Even though it is the inevitable result of living..." - VS Imaginator (Boogiepop Returns: VS Imaginator Part One Chapter Four)
- "It is easy to become carefree. All you have to do is lose your soul." - VS Imaginator (Boogiepop Returns: VS Imaginator Part One Chapter Five)
- "Not all confusion will ever be cleared up. Sometimes it will solidify, still confused, and attempt to judge the world. Like a curse, affecting the world with no rhyme or reason..." - VS Imaginator (Boogiepop Returns: VS Imaginator Part One Chapter Six)
- "There certainly is something out there. Something that makes people believe that they have to know their place in life. This knowledge gets in between people, and rocks the very foundations of this world." - VS Imaginator (Boogiepop Returns: VS Imaginator Part One Chapter Six)
- "...If there is anything that gives value to human life, it is the struggle with that "something." In the battle with the Imaginator that does your thinking for you-VS Imaginator is the starting line on which all humans must stand." - VS Imaginator (Boogiepop Returns: VS Imaginator Part One Chapter Six)
- "A new possibility... occasionally consumes all things like itself... before self-destructing." - VS Imaginator (Boogiepop Returns: VS Imaginator Part Two Prologue)
- "Nightmares begin before you are aware of them. They are extremely difficult to predict or prevent." - VS Imaginator (Boogiepop Returns: VS Imaginator Part Two Chapter One)
- "Rather than ask yourself if you are correct, it is far more realistic to think about how you are mistaken. Most humans have not been designed to be right very often." - VS Imaginator (Boogiepop Returns: VS Imaginator Part Two Chapter Two)
- "When humans think something is absolutely correct, in most cases, that truth is already in the past." - VS Imaginator (Boogiepop Returns: VS Imaginator Part Two Chapter Three)
- "...but all hopes, ultimately, are achieved in the future. Everyone dreams, desires the realization of those dreams, but it is not the dreamer that obtains that realization. It is the following generation. Furthermore, for those that receive the fruits of that success, it is no longer a dream, but established fact. All hopes must therefore become the sacrifice of the victor, but this is how humanity has advanced. Our only road is ahead of us, for people cannot live in the past..." - The Victor's Principle: The Victim's Future (Boogiepop Returns: VS Imaginator Part Two Chapter Three)
- "Once something has begun to crumble, there is nothing to be done but rebuild from square one." - VS Imaginator (Boogiepop Returns: VS Imaginator Part Two Chapter Four)
- "A perfect victory is difficult to obtain. But it is even more difficult to lose well." - VS Imaginator (Boogiepop Returns: VS Imaginator Part Two Chapter Five)
- "Just as no truth is certain, there is no such thing as a perfect lie." - VS Imaginator (Boogiepop Returns: VS Imaginator Part Two Chapter Six)
- "In the End, there is nothing waiting for you." - VS Imaginator (Boogiepop Returns: VS Imaginator Part Two Chapter Seven)
- "Unfortunately, genuine effort is never understood by others. It is only understood when you emerge victorious, but when you win, the beauty of the effort extended is subverted into something else entirely. The true fruits of effort lie only within that which is sacrificed." - The Victor's Principle: The Victim's Future (Boogiepop at Dawn Chapter Three)
- "Nagi, what do you think being normal means? Being normal means abandoning change... staying exactly the same forever. So if you don't want that... then you have to be something that isn't normal." - Seiichi's dying words to Nagi (Boogiepop at Dawn Chapter Three)
- "It is a mistake to say that humans see only what lies in front of their eyes. They do not even see that." - When a Man Kills a Man (Boogiepop at Dawn Chapter Four)
- "Whenever you are hiding something from other people the world is hiding ten times that much from you." - The Proliferation of 'Dunno' (Boogiepop at Dawn Chapter Four)
- "If you are a warrior, born to fight, then the object of your life's purpose exists only within the enemy." - Isolation and Faith (Boogiepop at Dawn Chapter Four)
- "If there is such a thing as a God, then that God would only exist in the future." - VS Imaginator (Boogiepop at Dawn Chapter Four)
- "Humans do not possess a single, focused will. In their hears, they have countless bugs, buzzing in all directions. There are times when all these bugs pounce on the same food, but when they are focused on different desires, people take actions that can only be described as incoherent." - When a Man Kills a Man (Boogiepop at Dawn Chapter Six)
I think somewhere else in the anime, another episode has a couple more quotes. But I can't find the post-it note I'd written them down on, and I just don't have the time to rewatch the entire series anytime soon. They'll be added in when relocated, I suppose.
The main purpose of this post was to give players blanket permission for their characters to have heard of Kirima Seiichi and even have read his books. Either the characters' worlds overlap with the Boogiepop-verse, or they saw/read the copies of his works that mysteriously happen to be in the camp library. Woo.