美夜月鏡 (Miyagekkyō) is an instrumental composition by かゆき (Kayuki), originally created for Sega's ONGEKI R.E.D. and later brought into maimai でらっくす PRiSM through the ongoing cross-title collaboration between ONGEKI, CHUNITHM, and maimai. The track is driven by a crisp piano melody and bright brass accents, performed by yoa (dawn-system), giving it an energetic yet atmospheric character at 164 BPM. The title uses the kanji 美 (beauty), 夜 (night), 月 (moon), and 鏡 (mirror), read with the coined reading みやげっきょう (Miyagekkyō), a non-standard reading that departs from conventional kun'yomi or on'yomi. The song debuted in ONGEKI R.E.D. on March 11, 2021, as part of Chapter 4, Chapter 3 輝く、三つ星 (Shining, Three Stars), where players could unlock it by achieving 1200% total damage against opponent 藍原 椿 at level 55. It later became available by default in ONGEKI R.E.D. PLUS. Its arrival in maimai on September 12, 2024, was tied to the ONGEKI bright MEMORY Act.3 linked-song campaign: players with a linked Sega account could unlock it simply by playing ONGEKI once. From December 6, 2024, the song became available by default to all maimai players. The Asian version followed on March 13, 2025, and the Chinese version (舞萌DX 2025) on January 23, 2026. In maimai, the track features DX-mode charts designed by two notable creators: the Expert chart (level 12) by はっぴー (Happy), and the Master chart (level 14, constant 14.1) by ロシェ@ペンギン (Rocher@penguin), the same designer who handled the Master chart for this song in ONGEKI. With 1,011 total notes, the Master chart stands out for its dense construction and heavy Touch-note layout.