ヤミツキ (Yamitsuki) is a dark electronic Vocaloid song by producer MARETU, sung by Hatsune Miku, that entered maimai でらっくす PLUS on January 23, 2020. The title is a layered pun, it simultaneously invokes 病み付き (yamitsuki, "addiction" or "obsession") and 闇月 (yami tsuki, "dark moon"), a wordplay that mirrors the song's lyrical fixation on pain, sadism, and a distorted kind of euphoria. The song runs at a brisk 208 BPM for 2 minutes and 29 seconds, characteristic of MARETU's high-energy, dissonant production style. ヤミツキ belongs to the Kotonoha Project (言ノ葉Project) 2nd Season, where it is classified as Side Story Essence 1. Its official music video was created by the collaborative duo suckerpunch / しきみ, whose stark visual style complements the track's oppressive atmosphere. Beyond maimai, the song also crossed over into SEGA's other rhythm game franchises, CHUNITHM NEW (2022) and オンゲキ R.E.D. (2020), marking the first Kotonoha Project track to appear in オンゲキ. In maimai, the Expert and Master charts were designed by サファ太 (Safata). The Master chart originally launched at level 13 but was adjusted downward over successive version updates, eventually settling at 12+ (constant 12.7) from the FESTiVAL version onward. The chart is known for its dense Tap-heavy patterning at high speed, with 499 Tap notes among a total count of 724, plus a generous 70 Touch notes that demand precise spatial awareness during the song's relentless 208 BPM drive.