Sweet Requiem is a collaborative arrangement by REDALiCE and aran, reimagining "少女綺想曲 ～ Dream Battle" (Maiden's Capriccio ~ Dream Battle), the stage 4 boss theme and Reimu Hakurei's character theme from Touhou 8: Imperishable Night (東方永夜抄). The original composition by ZUN (Team Shanghai Alice) was rearranged into a driving electronic track for the doujin album SELECTiONS, first released at the 2017 Hakurei Shrine Grand Festival (博麗神社例大祭), the largest annual Touhou doujin event. The song entered SEGA's rhythm game lineup through CHUNITHM CRYSTAL PLUS in September 2020 before arriving in maimai DX Splash on February 5, 2021. It sits in the 東方Project (Touhou Project) category and is purely instrumental, driven at a steady 190 BPM across its 2:01 duration. The Master chart, designed by 隅田川星人 (Sumidagawa Seijin), demands dense execution with 908 notes at level 13+, while the Expert chart by サファ太 (Safata) provides a level 10+ intermediate challenge. The jacket art depicts Reimu Hakurei based on the SELECTiONS album illustration, rendered as a standalone visual, the same design used for the song's SOUND VOLTEX appearance.