Eien no Melody (永遠のメロディ, "Eternal Melody") is a Touhou Project arrange track by the doujin circle unit あ～るの～と（いえろ～ぜぶら）, an alias operating under the long-running Touhou arrange circle Yellow Zebra (いえろ～ぜぶら). The song reworks Fujiwara no Mokou's boss theme "Reach for the Moon, Immortal Smoke" (月まで届け、不死の煙), which originates from Touhou Eiyashou ~ Imperishable Night, the eighth mainline Touhou title, known for its moonlit atmosphere and themes of immortality. The track joined maimai MiLK on May 8, 2018, toward the tail end of the pre-DX cabinet era, before Sega introduced touch-screen gameplay. Because of this timing, all four standard charts for Eien no Melody use only Tap, Hold, Slide, and Break notes, with no Touch-note patterns. The 155 BPM arrangement channels the brisk, melody-driven energy that Yellow Zebra's doujin output is known for. The song's difficulty levels were adjusted upward across subsequent maimai version updates as the game's overall difficulty ceiling rose. The Expert chart, designed by 玉子豆腐 (Tamago Tofu), progressed from 8+ through 9 and eventually to level 10. The Master chart, designed by サファ太 (Safata), climbed from 10+ to 11+ and settled at level 12 with a constant of 12.5, a mid-to-upper Master tier that offers a substantial challenge.