Demon Slayer: To the Infinity Castle Transformed – Animenz’s Epic Piano Arrangement

<Demon Slayer> is a dark fantasy manga series written and illustrated by Koyoharu Gotouge, serialized in Japan since 2016. The story centers on the conflict between demons who prey on humans and the Demon Slayer Corps, an organization dedicated to hunting them. After losing his family and witnessing his younger sister Nezuko turn into a demon, the protagonist Tanjiro joins the Demon Slayer Corps in hopes of turning her back into a human. As he faces countless battles, the narrative unfolds through numerous hardships and trials.

With its striking action sequences, emotionally rich storytelling, and philosophical contrasts between life and death, the series has resonated deeply with audiences worldwide. Following its anime adaptation, Demon Slayer achieved explosive global popularity. Demon Slayer: Kimetsu no Yaiba – The Movie: Infinity Castle, which premiered in July 2025, was met with great enthusiasm not only in Japan and South Korea but also in the North American market, achieving remarkable box office success with a global audience count approaching ninety million viewers.

Plot Summary of Demon Slayer: Infinity Castle

As the final confrontation with Muzan approaches, the Demon Slayer Corps is suddenly drawn into an unknown space known as the “Infinity Castle” through Muzan’s scheme. The Infinity Castle is a vast structure where the concepts of up, down, left, and right collapse, created by Muzan and the Upper Rank demons to gain the upper hand in battle. Inside the castle, the Demon Slayers are scattered, each forced into one-on-one or small-scale battles against the Upper Rank demons. Carrying both his anger toward Muzan and a clue that may lead to Nezuko’s return to humanity, Tanjiro confronts these powerful enemies.

The battles within the Infinity Castle go beyond simple victories or defeats. They present a series of confrontations where the obsessions, choices, and beliefs of humans and demons collide head-on. As the fighting intensifies, the Demon Slayer Corps is pushed closer to its limits. However, through their interconnected resolve, they begin to carve a path toward Muzan. The fierce struggle within the Infinity Castle ultimately becomes a crucial turning point leading to the final battle.

<To the Infinity Castle> by Go Shina

<To the Infinity Castle by Go Shina>

One of the most iconic OSTs that runs through this story is To the Infinity Castle by composer Go Shina. Upon first hearing this piece, one is immediately struck by an overwhelming sense of standing before a massive gate. Go Shina expands the scale of the scene through the use of a large orchestral ensemble combined with choir, creating not merely background music but a fully narrative musical moment.

The heavy sounds of percussion and brass build tension, as if foreshadowing an imminent threat, while also signaling the beginning of an unavoidable large-scale battle. Above this, the rapidly moving string accompaniment evokes the chaotic moment in which the heroes are drawn into Muzan’s fortress—an intricate, maze-like space—by demon blood arts. The music relentlessly drives forward, mirroring the distortion of space and the characters’ loss of orientation.

In the latter half, the orchestral sound becomes even richer. With drums at the core, choir, piano, synthesizer, strings, and brass all join together to perform the melody, leaving the impression of a grand declaration marking the beginning of a long war.

Animenz’s Piano Arrangement of To the Infinity Castle

Can this spectacular sound truly be transcribed to the piano? The piano arrangement of

<To the Infinity Castle> by Animenz, which will be focused today, faithfully preserves the dark and tense atmosphere of the original while remaining structurally true to it. At the same time, it vividly recreates the distinctive characteristics of the various instruments used in the original version on a single piano.

<To the Infinity Castle - Piano Arrangement by Animenz>

Tremolo and the Sense of Approaching Drums

At the end of the introduction, which begins with the original melody, a tremolo appears in the left hand. Tremolo refers to a technique in which the same note is played rapidly. On the piano, tremolo often requires alternating between notes an octave apart using the outer fingers, making control of the arms and wrists crucial and the technique quite demanding. In this introduction, the tremolo gradually grows from a soft dynamic to a stronger one, resembling distant drumbeats drawing closer, and serves to announce the beginning of the big event in the music.

Ostinato as a Driving String Texture

The ostinato that appears throughout the piece refers to a method of continuously repeating a short rhythm or pattern. In the original track, this role is primarily carried by the strings, driving the overall flow of the soundtrack. In Animenz’s piano arrangement, however, the ostinato requires a more advanced level of technique. While the same pattern continues, the tension evolves as the register and hand positions change in the first half. The ostinato pattern, which begins in the left hand, shifts to the right hand in the following section (00:51) and is played using a short, detached staccato touch. This evokes the spiccato technique in string instruments, where the strings are lightly bounced and articulated by delicately controlling the bow.

A Delicate High Register Suggesting a Synthesizer

As the piece progresses toward the latter half, the music becomes increasingly elaborate. Around the 2:00 mark, there is a passage that imitates the synthesizer sound of the original track through rapid sixteenth-note runs in the extremely high register. In this section, while the right hand moves quickly in the upper register, the left hand must delicately perform arpeggios and block chords simultaneously. Although the dynamic is marked p (soft), the passage is highly dramatic and technically demanding, requiring extensive practice.

A Hidden Timbre: The Role of the Thumb and Inner Voice

In the section labeled L (3:10), the main melody from the original track reappears in the right hand. Here, the performer must clearly project the top melodic line while simultaneously managing a wide-ranging left-hand part, demanding a high level of concentration. In the following M section (3:44), the main melody shifts to the middle register, or inner voice. At this point, rather than focusing on the visually apparent right-hand and left-hand parts, the performer must carefully bring out the inner melodic line, which is often played by the left-hand thumb. This makes the passage particularly challenging from a technical standpoint.

Conclusion

The piano is often referred to as a “small orchestra,” and overall, Animenz’s arrangement exemplifies this idea by allowing the piano to showcase a wide range of timbres as if it were an entire orchestra. Beyond presenting a simple melody, the arrangement expands the piano’s tonal palette to encompass the characteristics of percussion, strings, winds, and even synthesizers, while remaining structurally faithful to the original composition. Would you like to challenge yourself by performing this score? Click the link below to view the sheet music.

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