This page contains spoilers from the light novel! Read at your own risk.
"I was the last one left back then, and that's how it's always been till now. That's why I have to take them with me. I'll take everyone who fought and died alongside me to my final destination." ― to Lena, regarding his promise.
His Personal Name is Undertaker (アンダーテイカー, Andāteikā?).
He is the leader of the Spearhead Squadron, as well as the default operations commander of the Eighty-Sixth Strike Package. Among the Eighty-Six, he is known as the Reaper (死神, Shinigami?) of the Eastern Front. His ability to hear the voices of the Legion designated him as a high-priority target with the callsign of Báleygr (バーレイグ, Bāreigu?).
Shin has the bloodred eyes of a Pyrope and the jet-black hair of an Onyx. His pale features and slender physique are characteristic of the Giadian Empire's nobles. He is described to be rather handsome, attracting the attention of a few of his female comrades.
Shin almost always wears a sky-blue scarf to conceal the jagged scar on his neck. He obtained this scarf from the captain of his first squadron. Before he was gifted the scarf, his scar was concealed by bandages.
As the Spearhead Squadron's leader, he wears a desert camouflage uniform scavenged from an abandoned Republic military depot. He later switches to the Federacy's steel-colored panzer jacket dress uniform, which generally does not allow for modifications. The combat flight suit however is much more lenient, allowing for Shin to wear his trademark scarf.
Shin is an incredibly kind person, even after being wronged by so many people in his life. He considers himself to be at fault in the matter with his brother and believes he is the one that needs to apologize. Even after being ostracized and feared by the other Eighty-Six, Shin felt that it was his responsibility to shoulder the deaths of his comrades and let them pass peacefully into the afterlife.
He had always been the only person left alive until he met Raiden Shuga. Thus, even after meeting a companion that could survive along side him, he always felt it was his duty as the survivor to silently carry the tags of the fallen to his final destination. Even once letting go of his fallen comrades on the border between San Magnolia and Giad, he still used his comrades' deaths as an excuse to return to the battlefield.
Shin's ability to hear the voices of the Legion places enormous mental strain on him, even when he has become accustomed to listening to the constant wails of the dead. The weight of both his responsibilities and the effects of his ability have contributed to his stoic nature and lack of mirth. Despite that, he has a gentle side to him that usually comes out when interacting with Fido.
His kindness also manifests in selflessness to an extreme degree. This is demonstrated in when he chooses to face the Shepherd alone to put his brother to rest, as well as when he forcibly takes control of the Spearhead Squadron's last Juggernaut and attempts to hold off the Legion so that the rest of his squadron can escape.
Shin had a distinct lack of care for himself. He compared himself to the Legion, calling himself a ghost, aimless and wandering. Consequently, he often threw himself into dangerous situations without regard for his own safety, somehow surviving through luck and combat skill. This tendency grew worse once Shin had completed his mission of putting his brother to rest and losing his raison d'etre.
Even once he reunited with Lena and was pulled out of his suicidal craze, he still could not fathom that he was allowed to be selfish. He believed he could live even without a future to look forward to, or happiness which he could call his own. When Lena asked him for a wish he wanted fulfilled, he couldn't think of anything. His answer in the end was to take Lena to the sea, which he admitted was probably different than what Lena's question had intended.
Shin eventually did realize his feelings for Lena. Once he confessed them to her during their stay in the Alliance of Wald, he was noted to be free of the shackles of pride binding him to the Eighty-Sixth Sector. He now genuinely has a future to look forward to, as well as a new found attachment to the world and humanity.
Shin is known as the Reaper of the Eastern front, a practical legend among the Eighty-Six. Both a moniker of reverence and fear, those who were assigned in the same squadron as him dreaded their fate of certain demise, or accepted that they would die knowing Shin would carry on their memory. No one would survive long term in a squadron with Shin present, no one except the one known as Wehrwolf.
Shin is often compared to a plague bringer or a prophet of death. His notoriety would spread from the word of his previous mechanics or squad mates which were transferred out of his squadron, such as Rito Oriya. His reputation would achieve a similar status in the central Republic military, due to stories of him breaking his Handlers and driving some to suicide through his ability to hear voices of the dead.
After entering the Federacy military, Shin soon earned a similar fearsome reputation due to his cold demeanor, headless skeleton mark, and exceptional combat skills. He also earned the jealousy of many junior officers due to his relatively fast promotion. He was initially mistaken for royalty due to his mixed Pyrope and Onyx heritage, and was often provoked into fights which he would win easily.
Born on May 19th RY 351 / SY 2132, Shin lived with his family in the First Sector of the Republic before the war with the Giadian Empire began. It is implied he lived a sheltered life, surrounded by "only kindness and affection". He also appeared to have developed his extrasensory ability early on, hearing "voices that spoke without words" from his family. He would often play with the daughter of his father's colleague, Henrietta von Penrose, whom Shin called Rita.
Shin and his family were forced to relocate to an internment camp when the war began due to the Republic's discriminatory policies. Shin's father was first to enlist in the Republic military, accepting the Republic's promise that Shin and the rest of his family would have their rights restored in exchange for military service. Despite this, the Republic does not uphold its promise. Upon delivering the news of Shin's father's death, it informs Shin's mother that the military service was in exchange for only one person's citizenship. Continuing to trust the Republic, Shin's mother also enlists to protect her sons, leaving eight-year-old Shin and his eighteen-year-old brother Shourei in the care of an Adularia priest, a friend of the Nouzens who had resisted the Republic's policies and remained in the village-turned-internment-camp's church.
Shortly afterward, Rei receives notice of his mother's death on the battlefield and an enlistment form for him, proving the Republic's promise to be a lie. Shin, to whom the concept of death was not yet comprehensible, implores Rei to explain why their mother would not be returning. Shin's pleas caused the grieving and frustrated Rei to snap and choke Shin in a fit of violent rage. Rei brings Shin to the brink of death before the priest intervenes and resuscitates him. Shin is left with a jagged scar around his neck as a reminder of his brother's hatred. The near-death experience also opens Shin's telepathic ability to a broader range of human consciousnesses, including those of the Legion, by temporarily experiencing the post-mortem collective consciousness of humanity. Rei avoids Shin after the incident and refuses to say farewell or even glance at Shin when he enlists and leaves Shin behind with the priest.
The life in the internment camp was particularly harsh for Shin. In addition to the terrible condition of the camp, Shin was also discriminated by other Eighty Six due to his Giadian noble blood. Hence, the caretaker priest, who was a former soldier of Republic's army, decided to teach Shin how to fight. 
Four years after Rei's enlistment, Shin hears his brother's voice among the laments of the Legion and realizes that Rei is dead. On that day, Shin enlists with the military and becomes a Processor.
A genetic feature that is seen in people of Pyrope heritage, specifically the Maika Clan. Those with the extrasensory ability can communicate with family members by hearing their thoughts. This ability makes use of the part of the brain known as the Night Head and is the basis for the Para-RAID's communication abilities. The range and limitations of the ability are unspecified in people other than Shin.
In Shin's case, his ability was originally restricted to only his family, the same as others with the ability. However, during his near-death experience after being attacked by his brother, Shin's consciousness temporarily entered the abyss of death, and he was able to hear the voices of those who had died. Upon being resuscitated, Shin retained the power to hear the voices of the dead that were still among the world of the living. The ability allows him to detect the Legion because the Legion was designed with the human neural system as a basis for their central processing system. While the Legion's original replica processors are not as easily detected by Shin, being more of an electric haze to his ears, the Legion's processors which have derived from the neural systems of dying Eighty-Six create easily distinguishable, and haunting, voices that Shin can hear.
The voices Shin hears can be transmitted through the Para-RAID. Shin has traumatized many incompetent and abusive Handlers with the haunting voices of the Legion, albeit unintentionally for the most part. By turning the synchronization rate of his Para-RAID to the maximum, he drove one particularly abusive Handler to suicide. When linking with other Processors, Shin turns the synchronization rate lower. The transmission of voices also allows linked Processors to determine the positions of nearby Legion using the voices' distance and direction.
Shin has a good grasp of military tactics and strategies, despite never receiving any formal training or education. During his time in the Eighty-Sixth Sector, Shin is able to analyze Legion deployment patterns and formulate an interception plan accordingly, allowing the Spearhead Squadron to operate effectively even in the absence of handlers.
Shin is also very observant. During the short period they lived together, Shin managed to correctly guess Frederica's true identity based on clues like the way she was treated, as well as Frederica's conduct and speech unfit for her age. 
Even during his first sorties with only one month of training, Shin's maneuvers, judgment, and decision-making were well above what was expected of him. Although he had never experienced combat before, his instincts as an Onyx immediately kicked in, granting him a precise awareness of the battlefield. His awareness extended beyond what is normally possible, to the point that he was aware of the movements of the enemy's reload system.
Currently, Shin's combat skills are unmatched by other Processors, as he has honed his skills to levels far above the other veterans. Combining his reflexes and telepathic ability, he can perform attacks that no other Processor can do, such as charging three Löwe at once in a frontal attack. His Undertaker is specialized for his melee-oriented combat style, replacing its standard machine guns with high frequency blades, with all of its limiters being broken to maximize mobility. Due to this, however, there are situations where he could be completely useless against long ranged targets once his main smoothbore gun ran out of ammunition.
His capabilities as a Feldreß pilot are weaker when fighting fellow humans, however, as he isn't used to fighting opponents he can't hear with his ability. This is proven during his time in the Alliance of Wald, where he was able to be matched by Olivia Aegis during their training simulations.
Shin is also proficient in hand-to-hand combat, taking down the much larger Raiden in a fistfight and stating that he could disarm and kill three Republic soldiers before they can even remove their safeties. Even in his earlier years as a Processor, his bullies didn't dare touch him due to fearing his strength. His proficiency in various forms of combat ties back to his heritage as a Nouzen, an Onyx clan that served as the Giadian Imperial guard.
Federica herself believes that Shin is one of the most skilled warriors, if not strongest, in his clan's history. His combat skill is exceptional even compared to the Giadian Imperial guard, of which many also came from the Nouzen clan.
"This is the best outcome I could have hoped for, but you guys got the short end of the stick... What will you do? Knowing that you'll die tomorrow, will you hang yourself today?" ― to Raiden, regarding the Special Reconnaissance Mission and their upcoming battle with Shourei.
"If, one day, you make it to our final destination, would you please leave flowers?"― to Lena, handwritten on a piece of paper.
"It's been a while, Handler One." ― to Lena, reunion at the Processor memorial.
- Shin is known to be an avid reader, reading various types of books to take his mind off of the voices of the Legion. The literature Shin reads are references to works or events that influenced the author during her writing of the novel. The literature he is known to have read are:
- All Quiet On the Western Front by Erich Maria Remarque (Volume 1)
- Second Variety by Philip K. Dick (Triage - Black Tag)
- The Mist by Stephen King (Triage - Black Tag)
- Takasebune by Mori Ōgai (Volume 4)
- Mein Kampf by Adolf Hitler (Triage - Black Tag)
- The Bible (Volume 1)
- Thou Shalt Not Die by Akiko Yosano (Triage - Black Tag)
- The Principles of Quantum Mechanics by Paul Dirac (Manga Chapter 7)
- Moby-Dick; or, The Whale by Herman Melville (Episode 4 BD version)
- Shin carries around a 9 mm pistol which he obtained from Isuka. He uses the sidearm to euthanize his comrades that have been mortally wounded. The motion of cocking the gun and aiming to put his comrades out of their misery is second nature to him, a habit he would carry even outside the Eighty-Sixth Sector. He claims that he has no attachment to the weapon.
- By possessing both the enhanced martial prowess of an onyx and psychometry of a pyrope, Shin is the only known esper that has two special abilities so far.
- His cooking is bland and unappetizing due to his lack of care, though he is adept at using a knife.
- Shin knows how to sew, having learned the skill to repair his clothes. He often has to help Kurena with mending her clothes, though this may just be a ploy by Kurena to get a chance to talk with him more often.
- Shin is referred to as Báleygr by the Legion, a name of Odin meaning "Flaming Eye". The various parallels between Shin and Odin include:
- Both Shin and Odin have red eyes, although Odin only has one.
- Shin gained his ability to hear the Legion on the verge of death. Odin gained his power and wisdom through the same means.
- Shin collected the tags of his fallen comrades into a box, while Odin collected the souls of esteemed warriors in Valhalla.
- Shin is Lena's romantic partner, while Odin is Freyja's husband. Within the Strike Package, Lena commands the unit from a vehicle known as the Vanadis, another name of Freyja. It is also said that Freyja receives half of the fallen warriors in Fólkvangr, while the other half goes to Valhalla. With the addition of the anime, Lena's box of doodles could be seen as the Fólkvangr to Shin's Valhalla.
- Shin is the leader of the Eighty-Sixth Strike Package, which deploys an armament called the Mk. 1 Armée Furieuse. The Armée Furieuse is French for the "Ghost Riders", an alternate name of the Wild Hunt which was led by Odin.
- "Shin" is word play on the Japanese word for "Death" (死, Shi?) and the English word "Sin".
- Shinei Nouzen can be rendered in kanji as 真瑛 凌霄, Shinei meaning "True Crystal" and Nouzen being derived from "Nouzenkazura". Note that the canon spelling of his name is in romaji, the novels in Japanese use katakana, while the kanji spelling has never been used within the novels.
- Despite what he said to Lena in Episode 6, Shin does not like sweets. This is due to Anette kept giving him her horribly made desserts during their childhood.
- Shin's internment number is E022-23093.
- Shin has a dismissive attitude towards maintaining the condition of his Feldreß, which he abuses constantly during battle. This aspect of him lead to many arguments with his mechanics.
- Shin has an unusual ability to do be completely silent as he walks and moves around, also extending to other things like opening doors. This trait is also shared by his father and brother.
- Shin's characterization is very similar to Akito Hyuga, the protagonist of Code Geass: Akito the Exiled. The various parallels between Shin and Akito include:
- Both of them are ace pilots and leaders of a suicide squad of a race treated as sub-humans by their home country.
- They pilot white-colored quadrupedal mechs, and their combat style is to engage in fierce melee battles.
- They gained their special power to hear from the dead after their elder brother attempted to kill them in the past.
- It's their life goal to kill their brother on the battlefield.
- Their personal moniker are strongly related to the dead - "Undertaker" for Shin and "Ghost of Hannibal" for Akito, helped with the fact that they were often the sole survivor of their previous squadrons.
- Their love interest is a young girl with aristocrat background acting as their squad commander, and the first one to treat them humanely.
- Volume 1 Chapter 3
- Volume 1 Prologue
- Volume 3 Chapter 7
- Volume 10 Brand
- Dengeki Bunko Official Twitter Account
- Volume 6 Epilogue
- Birthday Special - Shin Continued
- Volume 2 Chapter 4
- Volume 2 Chapter 2
- Volume 7 Chapter 4
- Volume 9
- Volume 11 Epigraph
- Volume 10 Pledge
- Volume 10 Misericorde
- Volume 10 Undertaker
- Asato Asato Official Twitter Account
- Volume 2 Chapter 1
- Dengeki Bunko Official Twitter Account
- Volume 1 Chapter 2
- Dengeki Bunko Official Twitter Account
- CHARACTER | TV ANIME "86-Eighty SIX- Official Website
- Volume 5 Mechanical Design Illustration 2
- Volume 3 Chapter 9
- Volume 1 Chapter 7
- Volume 1 Interlude 3
- Volume 6 Chapter 1
- Volume 8 Prologue
- Volume 1 Chapter 1
- Volume 2 Chapter 5
- Volume 4 Prologue
- Volume 1 Chapter 4
- Volume 2 Chapter 3
- Volume 5 Chapter 4
- Volume 1 Chapter 5
- Volume 1 Chapter 6
- Volume 1 Epilogue 2
- 86 Side Stories - Volume 1 Special Edition Bonus
- Asato Asato Official Twitter Account
- 86 Side Stories Raiden's Birthday
- Episode 2