残響散歌 (Zankyou Sanka) is a song by Japanese singer-songwriter Aimer, released as her 20th single on January 12, 2022. It was composed and arranged by Masahiro Tobinai, with additional arrangement by Kenji Tamai. The track served as the opening theme for the Entertainment District Arc of the massively popular anime *Demon Slayer: Kimetsu no Yaiba* (鬼滅の刃 遊郭編), propelling it to become one of Aimer's most commercially successful releases. In maimai, 残響散歌 debuted on September 15, 2022, as part of the maimai でらっくす FESTiVAL launch lineup across Japanese, Asian, and Chinese regions. The song's driving rock instrumentation, soaring vocal melody, and emotional intensity typical of the *Demon Slayer* franchise make it an energetic pick for rhythm-game adaptation. Its Master chart, designed by Jack at a level-13 difficulty (constant 13.4), features dense slide-note sequences, while 翠楼屋's Expert chart (level 9+, constant 9.7) offers a demanding intermediate challenge. 残響散歌 was removed from the maimai DX series beginning in August 2025, first from the Chinese version on August 20, then from the Japanese version on August 22, and finally from the Asian version on September 5, making it a time-limited addition to the game's playable catalog.