Ichirohiko is the main antagonist of Mamoru Hosoda's 2015 anime film Bakemono no Ko (English: The Boy and the Beast). He is the adoptive older son of master swordsman Iōzen and brother to Iōzen's biological son, Jirōmaru. In the movie, Ichirohiko is the adversary of Kyūta, the apprentice of Iōzen's rival Kumatetsu.
He was voiced in Japanese by Mamoru Miyano (teenager) and Haru Kuroki (child), while in English he was voiced by Austin Tindel (teenager) and Morgan Berry (child).
Ichirohiko hopes to become a mighty swordsman, just like his father, but due to his personal doubt and realization of not being his father's "true son" Ichirohiko becomes consumed by the emptiness, a malevolent energy inherent only to human beings, which grants them supernatural abilities, but at the cost of their own sanity. With these powers, Ichirohiko sets out to murder Kumatetsu for having bested his father in combat.
He then sets his sights on Kyūta because he saw in him everything he could never be. However, with the help of Kumatetsu's god form, Kyūta successfully purges Ichirohiko of his emptiness and sends him back to his adoptive family with the hope that he could overcome his doubt.
When Ichirohiko was young, he envisioned his father as his idol. However, as he was growing up, he did not know about his true identity as a human and was ashamed of his appearance, as he wanted to be in the image of a boar like his father. During his childhood, Ichirohiko merely looked down on Kumatetsu for his rude and unkempt behaviour, as did most other citizens of the city. However, once he grew into a young man, Ichirohiko began despising Kumatetsu for being Iōzen's rival, while the thought of him beating Iōzen was unimaginable.
As a direct corollary to his hatred of Kumatetesu, Ichirohiko harbored an even deeper hatred for Kyuta for being Kumatetsu's apprentice and the only person who supported him. Ichirohiko's negative emotions were what led the emptiness inside him to consume him and later drove him to the edge of insanity as he killed Komatetsu and tried to kill Kyouta. In the end, after Ichirohiko was defeated by Kyouta, he awoke as a much more level-headed young man. He also noticed the bracelet on his wrist left by Kyuta that showed Kyuta's appreciation to him, something which Ichirohiko quickly took notice of.
Ichirohiko was very loving towards his brother, Jiromaru, and they would often spend plenty of time together in town. At first, Ichirohiko did not participate in the other childrens' teasing of Kyuta and instead told them to leave the human alone, albeit in a condescending town towards Kyuta. Ironically, Jiromaru grew up admiring both Kyuta and Kumatetsu while Ichirohiko learned to hate them. His hatred went so far as hitting Jiromaru for even considering that their father could lose to Kumatetsu.
Ichirohiko was a human baby, abandoned by his parents in an alley of a major Japanese metropolis until he was found by the beast nobleman, Iōzen. Despite his people's prohibition on allowing humans into their realm, Iōzen adopted the human infant and raises him in the Beast Kingdom as his first son. Sometime later, Iōzen and his wife had their second, biological son, Jiromaru.
One day, the Lord of the Beast Kingdom was planning to retire in order to become a god and would pass down his position as lord to either one of his two disciples, Iōzen, who is beloved for his honorable demeanor, and Kumatetsu, who is disliked for his stubborn attitude. However, the Lord of the Beast Kingdom demanded that both his disciples must first have at least one apprentice of their own as a sight that they are worthy of being a leader. To that end, both Ichirohiko and Jiromaru spent their youth training in the martial arts of kendo (swordsmanship) and kenpo (hand-to-hand-combat). Although their father did train them for the most part, his business as a nobleman would often keep him busy and away from his sons' training.
Iōzen had raised Ichirohiko with the belief that he was a beast, but as he grew up, the boy began questioning that he was Iōzon's actual son on account that he did not grow a snout and tusks akin to his father's. Despite Iōzen's assurance that he was in fact his son, Ichirohiko had trouble accepting the fact who he truly was. The reason why humans were traditionally forbidden from entering the Beast Kingdom was because they could be possessed by their own emptiness, a spiritual manifestation of their negative emotions, which, although offered them supernatural power, would also cause them to become hostile and possibly murderous. As such, Ichirohiko's self-loathing slowly turned into the emptiness in his heart all throughout his young life, usually manifesting as a form of low-level telekinesis. However, this was usually overlooked as being a kind of power which most beast sages could naturally obtain through training.
Ichirohiko appears for the first time in the movie at a marketplace with his father and younger brother, Jiromaru. There he noticed Kumatetsu's human apprentice, Kyuta, who was discovered by one of Iōzen's apprentices. Despite Iōzen's warning to Kumatetsu that bringing a human to their world was dangerous because of the darkness they carry in their hearts, Kumatetsu has known of it and claims that he has the right to train anyone he chooses, even if they are a human. As a result of their bickering, Iōzen and Kumatetsu enter into a heated fight, wherein the vast majority of the crowd roots for Iōzen, obviously including Iōzen's sons. The battle is won by Iōzen, but not until Kyuta roots for Kumatetsu and the Lord of the Beast Kingdom makes his appearance. The Lord of the Beasts permits Kumatetsu to train Kyuta in martial arts because his reason is that humans are not inherently evil. And although Iōzen must accept the Lord's wishes, his son's are less then compliant. Jiromaru begins bullying Kyuta for being a human, leaving Ichirohiko to break the fight but unknowingly belittling Kyuta by claiming that "how can someone so weak be dangerous!"
Late Teen Years
In the span of nine years, Kyuta does become an exceptional martial artist, which attracts several admirers and aspiring apprentices for Kumatetsu. Even Jiromaru gains a newfound respect for the human teenager, befriending Kyuta and frequently inviting him to his family's estate for snacks. Ichirohiko, on the other hand, grows up to become embittered and jealous at Kyuta's excellence and his own lack of bestial traits. He constantly covers up his face with a boar-shaped hat to compensate. In one instance he turns to his younger brother and angrily notices his snout and tusks.
Eventually, the day arrives when Iōzen and Kumatetsu must fight in order to determine which of them will became the new lord of the Beast Kingdom. The battle is viewed by the entire city. Kumatetsu and Kyuta had a brief falling out after the boy expressed his interest in returning to the human world, but the two soon reconciled after Kyuta (with the help of the human teenage girl Kaede) comes to terms with his past and his own insecurity. In contrast, Ichirohiko's embitterment got the better of him, resulting in him being completely overtaken by the emptiness in his heart.
Before the decisive battle, Ichirohiko punches Kyuta in the stomach and now openly expresses his hatred towards him and his master. He even goes so far as to hit Jiromaru for worrying that their father was losing to his adversary. Thanks to his pupil's confidence in him, Kumatetsu wins the fight and is proclaimed the new lord of the beasts. This unfortunately proves to be the straw that broke the camel's back, as Ichirohiko, now having been driven completely mad, uses his telekinesis to stab Kumatetsu trough the chest with his father's own sword. This in turn causes Kyuta to lose control of his own emptiness and nearly stabs Ichirohiko with the same sword, but is stopped at point blank range after noticing the string that Kaede wrapped around his left wrist, a charm meant to calm him down whenever he gets upset. In the middle of the event, Ichirohiko disappears to the human world, while Kumatetsu is put into medical care, with his condition being critical.
Kyuta overhears Iōzen's conversation with the Lord of the Beasts and the revelation that Ichirohiko had always been a human boy masquerading as a beast, who grew up angry at himself for not being able to match up to his father's image. Feeling sympathetic because of their similar backgrounds, Kyuta goes back to the human world in an attempt to rescue Ichirohiko from himself, realizing that given any other circumstances, Kyuta would have ended the same. Once Kyuta arrived in the human world, he returns Kaede the story of Moby Dick she gave to him as he was saying his goodbyes to her, although unable to explain the situation.
As Ichirohiko appears, the two fight on the streets of the human city, but after Ichirohiko begins using his shape-shifting and telekinesis to cause massive damage, Kyuta retreats to the subway alongside Kaede, with whom refuses to leave Kyuta. Kyuta and Kaede make their way to an empty urban park to ensure that no civilians get hurt. Just then Ichirohiko makes his appearance, now under the guise of a shimmering white whale with wild boar tusks after he discovers Kyuta's story of Moby Dick.
At first, Kaede chastises Ichirohiko for his rude behavior, telling him to grow up and not let his emotions consume him. Not having fazed the monstrous boy, Kyuta steps in and prepares to put his plan into action; he intends to absorb all of Ichirohiko's negative emotions inside his own heart and then stab himself in order to permanently rid Ichirohiko of his anger and hatred. Just then, however, Kumatetsu arrives in the form of a flaming sword, having reincarnated as a tsukumogami (Japanese for "tool god/spirit") and merges with Kyuta's heart, the purpose being to fight alongside his apprentice as one. With a newfound confidence and strategy, Kyuta uses Kumatetsu's godlike flames to purge Ichirohiko's heart of the young man's resentment towards himself and others.
Kyuta shares to an unconscious Ichirohiko that they are the same, both being human children whose fathers were beasts and hopes that Ichirohiko learns to live with himself. As a gesture of further kindness, Kyuta ties Kaede's string bracelet around Ichirohiko's left wrist. Ichirohiko wakes up the following morning in his bed back home, with his family standing beside him. He also notices the string bracelet left to him by Kyuta.
Ichirohiko possessed the emptiness within his heart, allowing him to have the power of telekinesis. With it, he can use it to create astral forms, such as manifesting himself into a whale after looking through Kaede's book about Moby Dick. He is also very skilled at sword fighting, as he was raised by his father, who is a skilled fighter.