Sui Ishida, the creator of the Tokyo Ghoul series, is a mastermind of foreshadowing and hidden details. The amount of characters and thus backstories and plotlines in the series is immense, but the detail does not suffer for it.
Tokyo Ghoul is one of the most thought-provoking and intricately planned manga. Here are 10 characters with hidden details about them that make them that much more interesting.
10 Arata Kirishima
The father of Touka and Ayato Kirishima, Arata, wanted only to live his life as a pacifist, trying his best to blend in with the humans. However, after the murder of his wife, his personality changed. In order to prevent any more loss and protect his remaining family, Arata cannibalized ghouls and humans to attain more power. Unfortunately, the CCG took notice and struck him down.
His kakuhou was harvested in a CCG lab and made into the Arata armor that Shinohara, Kuroiwa, Amon, Suzuya, and Abara have all donned at one point or another. During a fight against Ayato, Arata's son, Shinohara commented that the armor was "sluggish while fighting...possibly showing that the armor possesses a mind or will of its own."
9 Renji Yomo
An often forgotten detail in the Tokyo Ghoul series is that Yomo is related to both Touka and Ayato. Hikari Kirishima, their mother, was his sister, making him their uncle. Arima was the investigator to eliminate Hikari, creating Yomo's hatred and desire for revenge against him. In the Cochlea Raid arc, Yomo protects both Ayato and Touka against attacks from Arima, sacrificing himself and putting his life on the line to ensure their safety.
Though neither Arima nor Yomo were defeated in this fight, Yomo stated that if the investigator who took his sister's life was still alive and before him, he would not hesitate to take him out.
8 Uta
There's a lot of mystery surrounding Uta, even still after the series' completion. From his relationships with other characters to his motivations and true intentions, many questions remain unanswered. But, some details about him are a bit clearer than others, though still relatively unknown. For example, it is apparent that Uta has had various body modifications done on himself including tattoos and piercings. When questioned by Haise about what seems to be his forever activated kakugan, Uta claims that he had ink injected into his eyes to give them that appearance.
He also has tattoos covering much of his body. One in particular on his neck reads "Νεχ ποσσυμ τεχυμ ωιωερε, νεχ σινε τε." which translates to "I can not live with you, nor without you." This quote is in reference to his ghoulish nature, in which he relies on the humans that hate his kind in order to survive. With all of the questions revolving around him, one thing is known for sure: Uta is the most enigmatic character in the series.
7 Donato Porpora
This caretaker of a Catholic orphanage and the foster father of Amon Koutarou harbored a massive secret: he was a ghoul who murdered the children in his care. The orphaned Amon accidentally witnessed Donato feasting on one of his victims, one of Amon's young peers. Instead of killing him immediately, Donato spared Amon in a twisted form of fatherly love. When he was 12 years old, the CCG rescued Amon from the basement of the orphanage, taking him into their care.
As a result of his upbringing, it was natural for Amon to hate Donato. However, on multiple occasions throughout the series, it was unclear what his true feelings were. At the end of Tokyo Ghoul after his near-fatal battle with Kaneki, Amon recalls memories of his childhood with Donato and questions why his mind drifted to him. It is later revealed during the final fight between Donato and Amon that, despite all of the sufferings the ghoul had caused, it isn't wrong for a son to love his father.
6 Matasaka "Shachi" Kamishiro
Speaking of adopted fathers, it's often a forgotten detail that Shachi was once the adopted caretaker of Rize Kamishiro. He took her under his wing and decided to mentor her, treating her like his own daughter. However, as Rize got older and developed her disruptive eating habits, their relationship became strained. Shachi disapproved of her behavior, which ultimately leads to a raid by the CCG and Shachi getting captured.
Even with all of the tension between them, Shachi always viewed Rize as his child and made the ultimate sacrifice to protect her in the end.
5 Furuta Nimura
Initially, Furuta came off as quiet and altogether unimpressive character, but that changed rather quickly. After the Rose Extermination arc, his personality began to show as much more erratic, chaotic, and manipulative. Throughout the series, he was essentially able to operate in the shadows, associating with multiple different organizations including the CCG, the Clowns, V, etc. without anyone truly knowing.
During a conversation with Sen Takatsuki, aka Eto Yoshimura, after she revealed herself to be a ghoul and surrendered to the CCG, Furuta is mocked because he is unable to call his biological father such. Originally born as Souta Washuu-Furuta, there are hidden details within his name: the ghoul investigator was the illegitimate son of Tsuneyoshi Washuu, former head of the CCG. This taunting enraged Furuta, proving how deeply insecure he was about his lineage and consequential fate.
4 Juuzou Suzuya
By the end of the Tokyo Ghoul series, Juuzou is an incredibly powerful and capable leader, one of the CCGs finest assets. Though, his childhood was a completely different story. Kidnapped by the ghoul Big Madam, he was tortured in various different ways. He was forced to kill in the Ghoul Restaurant for Big Madam, whom he thought of, in a twisted sense, like his mother. She made him dress as a girl and was worried that he would "become ugly". To avoid that, she brutally castrated Juuzou against his will. By the time the CCG was able to rescue him, he was very deeply disturbed in every way possible, fundamentally unable to feel any emotions or pain.
Though, after many years of "normal life" as an investigator with the CCG, Juuzou was able to overcome the torture he endured. He even eliminated Big Madam, not as a result of his history with her, but simply as doing his job.
3 Tooru Mutsuki
Mutsuki was not raised by a ghoul, but his childhood was no easier than Juuzou's. Mutsuki, a transgender male who was assigned female at birth, was frequently subjected to punishment from his abusive father. It was even implied that his father sexually abused him. In a horrific massacre of his family that was deemed a ghoul attack, he was put into the custody of the CCG, though he remained emotionally unstable as a result of the abuse.
A while after Mutsuki becomes a member of the Quinx squad, he is captured by the ghoul Torso and held captive. The ghoul was obsessed with him, stating that they would get married, but he physically beat Mutsuki for being uncooperative. Torso reminded Mutsuki of his abusive father, which eventually sparked memories of murdering his entire family at the age of 12.
2 Ken Kaneki
Of course, the main character is going to have numerous hidden details about him! First and foremost, one of the most impressively foreshadowed hidden details was Kaneki's abusive mother. During the Rose Extermination arc, Haise's fight with Kanae was not looking good for him -- his dire injuries sent him into the recesses of his mind, where he found the white-haired child Kaneki. Haise, angered at being taunted by the child in his mind, attacks. As a result, the memories of his childhood abuse come flooding back, and he recalls that he wanted Arima to kill him at V14.
Even deeper, there is a bit of a conspiracy about what exactly happened when he was tortured by Yamori. Though never outright confirmed in the series and heavily disputed, some fans believe there are small hints that Yamori sexually assaulted Kaneki during the 10-day torture due to the ambiguity of what Yamori had done to his last victim, Kaneki's clothes change, his RC scans showing physical trauma, etc.
1 Kishou Arima
The undefeated investigator of the CCG, Arima always seemed to be the bad guy, the opposition to ghouls and the killer of Ken Kaneki -- sort of. It was only revealed in his dying moments that this wasn't the case. In fact, it was the exact opposite: Arima had been one of the good guys all along. A product of the Sunlit Garden, he was a ghoul-human hybrid with obvious immense strength, but health drawbacks as well. Though he was an infamous CCG investigator that had ended the lives of countless ghouls, Arima was secretly working with Eto to ensure Kaneki became the One-Eyed King all along.
Even though he came off as cold and uncaring, he truly did care for Kaneki and was happy that he was able to leave something good behind.