MAGNETAR GIRL is an instrumental track by Yu-dachi, originally appearing in the rhythm game ONGEKI as part of its R.E.D. PLUS edition before being ported to maimai でらっくす FESTiVAL. The song arrived in maimai on October 21, 2022, as part of the Touhou Project×ONGEKI collaboration area, where players could unlock it by accumulating 300 km of total distance in the event area. It became available by default starting from FESTiVAL PLUS onward. Yu-dachi was already familiar to maimai players at the time, having previously contributed the original song "白花の天使" (White Flower Angel) to the maimai series. Both compositions share the composer's characteristic high-energy electronic style, though MAGNETAR GIRL leans into a driving, synth-forward arrangement at a steady 170 BPM. In the maimai chart lineup, the MASTER difficulty (13+, constant 13.8) designed by たかなっぴー stands out for its heavy reliance on Touch notes, 128 out of 931 total notes are Touch inputs, giving the chart a distinctive tactile character compared to typical MASTER charts of the same level. The EXPERT chart (10+, designed by 翠楼屋) also incorporates a notable Touch-note count relative to its total note density. The song was later made available in Asian and Chinese versions of the game with region-specific unlock schedules.