CHAOS is a dramatic orchestral-electronic crossover track originating from Rayark's mobile rhythm game Cytus II. It was composed by the in-game unit Æsir, a fictional character within the Cytus II story who, in reality, represents a creative collaboration between two Rayark staff composers: Ice (Wilson Lam) and KIVΛ. The song was ported to maimai on June 11, 2020, arriving with the maimai でらっくす PLUS (DX PLUS) update as part of a collaboration event between maimai and the Cytus series. Running at 150 BPM with a duration of 2:30, CHAOS is an entirely instrumental piece, no vocals or lyrics accompany its arrangement. The track opens with tense, atmospheric string work before building into a soaring, climactic fusion of electronic beats and orchestral grandeur. A distinctive feature of the composition is its first half, which weaves together sampled melodic fragments from five songs from the original Cytus game: D R G, Hard Landing, Saika, Area184, and Biotonic. This gives the opening a medley-like quality that pays homage to Cytus's musical catalog. The song also appears in CHUNITHM NEW, where it is credited as Æsir「Cytus II」. In the Chinese version of maimai (舞萌DX), CHAOS was removed starting with 舞萌DX 2022, making it unavailable in that region's current arcade rotation.