"Kutsu no Hanabi" was released on June 28, 2017, as part of Yorushika's debut EP Summer Grass ga Jama wo Suru. Written and composed by n-buna and performed by vocalist suis, the track quickly became a signature example of the duo's lyrical and cinematic approach to songwriting. Its title, pairing the grounded image of shoes with the fleeting glow of fireworks, creates a metaphor for moments in life that are both ordinary and extraordinary-everyday steps framed against beauty that vanishes in an instant. The arrangement's blend of delicate stillness and swelling orchestration, combined with suis's emotive yet restrained delivery, resonated with young listeners who sought music that could capture both nostalgia and immediacy. Over time, the song became a favorite among fans who associate it with the emotional atmosphere of summer evenings and the quiet ache of transience. With a new interpretation by Teto Kasane, a long-loved virtual singer from the UTAU platform, "Kutsu no Hanabi" gains an additional dimension. Teto's voice, known for its balance of playful brightness and subtle emotional depth, reframes the song's melancholy with a sense of digital clarity and character-driven warmth. For those familiar with the original, her version offers a fresh perspective that preserves the song's core sentiment while introducing a new texture. For Vocaloid and UTAU enthusiasts, it is an opportunity to experience how a virtual performance can evoke the same kind of emotional response as a human voice, while bringing a distinct personality to the work. This convergence of a modern vocal synthesis icon with a song rooted in Japanese seasonal sentiment invites listeners to revisit its themes through both memory and novelty, allowing "Kutsu no Hanabi" to continue evolving in meaning with each performance.