モニタリング (Monitoring) is a Vocaloid track by DECO*27, one of the most prolific producers in the Vocaloid scene, featuring Hatsune Miku. The song originally appeared on DECO*27's sixth studio album TRANSFORM, released in 2024, and was brought to the arcade rhythm game maimai as part of the maimai でらっくす CiRCLE (maimai DX CiRCLE) update at launch in September 2025. Its presence extends beyond maimai: モニタリング also appears in CHUNITHM X-VERSE-X and オンゲキ Re:Fresh, making it a cross-title song playable across SEGA's three major arcade rhythm game series. The song's title and lyrics center on a surveillance theme pushed to an intimate extreme. The narrator claims omniscient knowledge of the subject's private moments, "きみがひとり"XX"してるの知ってるよ" ("I know you're doing XX alone"), blending possessive affection with voyeuristic curiosity. The recurring censored "XX" became an in-game wink when maimai's collection titles replaced it with "maimai" for a self-referential punchline. At a steady 132 BPM, the song's maimai chart set spans five DX difficulties. The Re:MASTER chart (level 13, constant 13.4), designed by カマボコ君, carries the highest density with 646 total notes. The MASTER chart (level 11+, constant 11.8) was crafted by 緑風 犬三郎, while the EXPERT chart (level 10+, constant 10.6) was designed by Jack. The Basic and Advanced charts have no credited designer.