DECO*27's 妄想税 (Delusion Tax) is a Vocaloid track that channels the producer's signature blend of satirical wordplay and pop-rock energy, delivered through Hatsune Miku's synthesized vocals. The title fuses 妄想 (mousou, "delusion" or "fantasy") with 税 (zei, "tax"), spinning a playful scenario in which wishful thinking and self-indulgent daydreams come with a price tag, a theme that resonated widely on NicoNico Douga, where DECO*27 established himself as one of the most influential Vocaloid creators of the early 2010s. In maimai, 妄想税 debuted during the ORANGE PLUS update and has since become a noteworthy case study in chart-level evolution. Its Master chart, designed by mai-Star, entered at level 10 and was incrementally re-evaluated through subsequent versions, climbing to level 11 during Splash, then to 12 by FESTiVAL, reflecting both the rising skill ceiling of the playerbase and the chart's own structural density. The Master arrangement leans heavily on Slide notes (63 out of 527 total), creating sweeping, continuous patterns that distinguish it from many of its level-12 contemporaries. The Expert chart, crafted by rioN, offers a contrasting experience at the 10+ tier with 399 Tap notes that test stamina and precision rather than slide fluency. The Basic and Advanced charts, while uncredited, provide accessible entry points into the song's rhythmic structure at levels 5 and 7 respectively.