忙シー日 (busY daY) is a maimai original song produced by Sasuke Haraguchi (原口沙輔) and featuring the vsinger Meguri Shikibu (式部めぐり). It was added to maimai でらっくす PRiSM PLUS on May 9, 2025, debuting as the Perfect Challenge target for Dragon Area 4 (ドラゴンちほー4). This commission marked Haraguchi's first original song written specifically for maimai, his earlier tracks 人マニア and イガク had already appeared in the series as licensed inclusions, but 忙シー日 was composed from scratch for the game's universe. Musically, the track is an energetic electro-pop piece driven by Haraguchi's signature production style: crisp synth leads, rapid-fire vocal chops, and repeated sample hooks. Fans of his earlier works will recognize the recurrence of the "ユ！" vocal sample (borrowed from イガク) and a "Drop it" voice clip, giving the song a self-referential, cohesive identity within Haraguchi's broader catalog. The vocals, performed by Meguri Shikibu, an electro-music-focused virtual singer making her maimai debut, deliver a relentlessly paced lyrical stream about rushing through a crowded, indifferent world without pausing to question its deeper mysteries. The song's flavor text, tied to the Dragon Area narrative, describes the inhabitants of Midgard living alongside dragons as partners. Though dragons possess vastly superior intelligence and potential, humans accept this coexistence without curiosity, unaware that it stems from an ancient pact. The lyrics echo this theme of surface-level busyness, a refusal to look beyond the immediate grind, with repeated refrains of "関係ナイ" (irrelevant) and "知らない聞かない要らない" (don't know, don't ask, don't need). The jacket art translates the title as "busY daY," using stylized capitalization that mirrors the song's chaotic, head-down energy. The music video was created by the artist Ehre_origine, who also animated the "ユ！" stone sculptures that appear during the sample, directly referencing the visual language of イガク's video.