ゴーストルール (Ghost Rule) is a high-energy VOCALOID track by DECO*27 featuring Hatsune Miku, originally released on the 2016 album GHOST. Composed and written by DECO*27 (Kosuke Terayama) with arrangement by Naoki Itai and an animated music video by 八三, the song drives forward at a relentless 210 BPM with sharp synth-rock instrumentation and rapid-fire verses. Its most instantly recognizable feature is an ascending-descending melodic hook, often textually rendered as 「おーお↓ーお↑ーお↓ーお↑ーお↓ーお↑ーお↓ーおぉー」, that became a beloved earworm across the VOCALOID fandom and beyond. Lyrically, Ghost Rule explores themes of self-deception, fractured identity, and the lingering "ghost" of a former self. The title itself is a Japanese wordplay blending "ghost" (ゴースト, gōsuto) with "rule" (ルール, rūru), evoking both a spectral law and the rules by which a hollow persona operates. The song made its rhythm-game debut in maimai MURASAKi on December 15, 2016, and was later ported to CHUNITHM STAR PLUS and オンゲキ, making it one of the most widely circulated DECO*27 tracks across SEGA's arcade rhythm-game lineup. In maimai, Ghost Rule is notable for having two distinct chart sets. The original Standard charts debuted with MURASAKi, while DX charts were added later in maimai でらっくす UNiVERSE (September 2021), initially gated behind a Stamp Card unlock campaign before becoming generally available. The DX Expert chart (designed by サファ太) and DX Master chart (designed by Jack) sit alongside Standard Expert (designed by 畳返し) and Standard Master (designed by しろいろ), giving players four high-level challenges across the two chart formats. The maimai in-game cut runs 2:10, shorter than the 2:29 edit used in CHUNITHM and オンゲキ.