Imperishable Night 2006 (2016 Refine) is a high-energy Euro Rave arrangement of "永夜の報い ～ Imperishable Night," the stage 4 theme from the Touhou Project title 東方永夜抄 ～ Imperishable Night (2004, composed by ZUN). The track first appeared in 2006 as a BMS (Be-Music Source) file under the alias 篠螺悠那 (Sasara Yuuna), and was remastered a decade later for its debut in SEGA's rhythm game CHUNITHM AIR, hence the parenthetical "(2016 Refine)" that sets it apart from the original release. The artist behind the arrangement, ゆうゆ / 篠螺悠那, operates across two creative lanes. As ゆうゆ (yuuyu), he is a Vocaloid producer known for hits such as 深海少女 (Deep Sea Girl), which also appears in the maimai series. Under the 篠螺悠那 name, he has produced numerous Touhou doujin arrangements and BMS compositions. For the 2016 remaster, illustrator tamajam contributed a brand-new jacket, giving the track a distinct visual identity from its 2006 predecessor. The arrangement is entirely instrumental, driven by a steady 161 BPM pulse, pounding kick drums, and cascading arpeggiated synth lines that typify the Euro Rave style. In maimai, the song was added with the FiNALE version on May 24, 2019, and has been carried forward through subsequent DX iterations. Its charts, particularly the Master and Expert difficulties, have seen multiple upward level revisions over the years as the game's difficulty calibration shifted, reflecting the track's sustained challenge relative to the evolving player base.