The Boy and the Beast

Nine-year-old Ren is grappling with the devastating loss of his mother, struggling to cope with the absence of parental support. He rejects the notion of living with his legal guardians and feels utterly alone in his sorrow.

In his deep grief, Ren escapes into the chaotic streets of Shibuya, where he faces the harsh realities of survival. He resorts to stealing food and sleeping in alleys, haunted by distressing memories of his mother's funeral.

Meanwhile, in the mystical Beast Kingdom, the grandmaster announces his intention to retire and reincarnate as a deity. He selects two potential successors, the dedicated Iōzen and the reluctant yet powerful Kumatetsu, hoping to inspire Kumatetsu to discover his true potential.

Kumatetsu, accompanied by his friend Tatara, wanders through Tokyo where they encounter Ren. Taking a gamble, Kumatetsu proposes that Ren becomes his disciple, inviting him into a world he never expected to enter.

Though initially resistant, Ren's curiosity about Kumatetsu's world draws him in. He eventually agrees to travel with Kumatetsu to the Beast Kingdom, where he soon realizes he cannot return to the human realm.

While in the Beast Kingdom, Ren witnesses a fierce clash between Iōzen and Kumatetsu. Despite the thrill of the moment, Kumatetsu suffers a swift defeat, leading the grandmaster to assure them that the crucial battle for succession is still to come.

Respecting Ren’s desire to keep his real name hidden, Kumatetsu names him 'Kyūta'. This marks the beginning of their journey together as master and disciple, deepening their bond as they navigate their new dynamics.

Kyūta engages in rigorous training sessions with Kumatetsu, learning the art of combat and gaining valuable skills. Their relationship transforms as Kyūta begins to mimic Kumatetsu during chores, enhancing his learning through observation.

Eight years later, a now-teenaged Kyūta emerges as a skilled kendo practitioner. Kumatetsu, inspired by his growth, gains newfound purpose and forms a supportive community, including the ambitious Jirōmaru who wishes to train under him.

Kyūta eventually discovers a way back to the human realm, reconnecting with his father and making friends with Kaede at school. Despite these connections, he struggles to reconcile his identity and experiences feelings of bitterness and alienation.

On the day of the highly anticipated succession duel between Kumatetsu and Iōzen, Kumatetsu falters without Kyūta's presence to support him. However, Kyūta ultimately reveals himself during the battle, motivating Kumatetsu to rise and confront Iōzen with renewed strength.

After Kumatetsu triumphs over Iōzen, it is revealed that Ichirōhiko, long considered merely a beast, was actually raised by Iōzen. Struggling with his identity, Ichirōhiko develops terrifying telekinetic powers, which begin to manifest threateningly against Kumatetsu.

As Kyūta grapples with his own emptiness and the temptation to unleash destruction upon Ichirōhiko, he finds clarity through the comfort of Kaede’s bracelet. This realization guides him towards embracing his true identity and purpose.

Embracing his destiny, Kumatetsu takes on the mantle of the new grandmaster, reincarnating as a sword to be handled with a heartfelt understanding. In this form, he fills the void within Kyūta, empowering them both to face the darkness that Ichirōhiko presents.

With the conflict resolved, Kyūta engages in a heartfelt conversation with Kumatetsu's spirit, exchanging promises of support. Ren's journey leads him to celebrate victory alongside Kaede and reconvene with his father, determined to forge a path forward carrying Kumatetsu's essence within him.