最終鬼畜妹フランドール・S (Saishuu Kichiku Imouto Flandre・S) is a blistering Touhou doujin arrangement by beatMARIO of the COOL&CREATE circle, reimagining Flandre Scarlet's theme "U.N. Owen Was Her?" from 東方紅魔郷 (Embodiment of Scarlet Devil). Clocking in at a relentless 200 BPM, the track captures the chaotic, unhinged energy its title suggests, "最終鬼畜妹" translates roughly to "final brutal little sister," a phrase deeply tied to Flandre's fandom identity as the sealed-away, emotionally unstable younger sister of Remilia Scarlet. Released in maimai FiNALE on May 24, 2019, the song quickly became one of the most recognizable Flandre-themed rhythm game arrangements, carrying forward beatMARIO's long history of high-energy Touhou arrangements in the broader BMS and rhythm game scene. The song arrived as part of maimai FiNALE, the final version of the original SD (STANDARD) cabinet line, and its charts have seen substantial level adjustments across subsequent DX editions, a testament to how the maimai team recalibrated difficulty expectations for this track as the series evolved. The Master chart (level 12, constant 12.1) carries exactly 666 total notes, a playful thematic nod to the song's devil-associated subject matter. The Re:Master chart (level 13+, constant 13.7) stands among FiNALE's most punishing challenges, designed by the anonymous 某S氏. A related, escalated arrangement titled 超最終鬼畜妹フランドール・S later appeared in subsequent maimai versions, extending the lineage of this fan-favorite Flandre theme.