This appears to be related to the (虜ノ調べ) series — a visual novel/adult game franchise by Argonauts / Atelier Sakura known for dark, plot-driven stories.
Furthermore, Toriko no Shirabe -refrain- if Aina no Shou -Cr- has contributed to a renewed interest in instrumental anime soundtracks, paving the way for other composers to explore the possibilities of music in anime storytelling. As a result, the anime community has been treated to a new wave of innovative and captivating soundtracks that continue to push the boundaries of the medium. Toriko no Shirabe -refrain- if Aina no Shou -Cr...
The game’s soundtrack features a leitmotif titled “Shirabe” (調べ), played on a out-of-tune piano. Each time Aina sings, the piano subtly corrects a note — representing the loop’s gradual decay. The includes a full vocal track sung by Aina’s voice actress, with lyrics that change during repeated playthroughs. Fans have decoded hidden messages in the spectrogram of the track, revealing the Keeper’s original name. This appears to be related to the (虜ノ調べ)