生命不詳 (Seimei Fushou) is an original song composed by 蜂屋ななし (Hachiya Nanashi) for maimai でらっくす Splash PLUS, featuring vocals by luz. The track arrived on May 28, 2021 as part of the Sky Street Area 2 unlock campaign, and carries a distinctive legacy within maimai's original song catalog: it is the final piece released under the Hachiya Nanashi pseudonym. Shortly after the song's debut, composer 栗山夕璃 (Kuriyama Yuri) announced the retirement of the alias, transitioning future work to their real name, making this track a thematic swan song for the moniker. Set at a brisk 200 BPM, the song blends driving electronic rock with emotionally charged lyrics written from the perspective of someone wrestling with regret, self-doubt, and the desire to start over ("もういっそ 最初からやり直させてくれよ", "Just let me start over from the beginning"). The vocals by luz deliver the introspective verses with an intensity that matches the tempo, while the instrumental arrangement layers sharp synth leads and aggressive percussion. An alternate version featuring the vocal synth v flower later appeared on the album Anaphylaxie Bee, released October 13, 2021. The accompanying in-game video and jacket art were produced by Wada Masako (松田綿雪) of Nanogram Inc., styled with a dark, nocturnal visual tone that mirrors the song's uneasy atmosphere. The game's flavor text ties the track into the Sky Street narrative, describing protagonist Akatsuki caught in a tense standoff with a hooded figure after learning that two allies have gone missing. In gameplay terms, the MASTER chart (designed by はっぴー) and EXPERT chart (designed by Jack) both demand strong endurance and precision at high speeds, consistent with the relentless 200 BPM foundation.