Natural Flow is a crossover track from Sega's 2000 arcade rhythm game *Crackin'DJ*, developed by Sega's Hitmaker division. The song was composed by Kentaro Koyama (credited as KENTARO「Crackin'DJ」) and arranged by Hiroshi Kawaguchi (Hiro), the veteran Sega composer best known for the *Space Channel 5* soundtrack. It entered the maimai song library with the PLUS update on January 17, 2013, marking one of the earliest instances of maimai drawing content from another Sega arcade rhythm game. Over its lifespan in maimai, Natural Flow has been through several genre reclassifications: it debuted under ANIME & GAME, shifted to GAME (GreeN through ORANGE PLUS), then SEGA (PiNK through FiNALE), briefly sat in ORIGINAL during the early でらっくす era, and finally settled into GAME & VARIETY (ゲーム＆バラエティ) from でらっくす PLUS onward. Its chart difficulty levels have also been revised upward across nearly every major version update, the Master chart, for example, has climbed from an original level 9 in maimai PLUS to its current 12+. The song's charting is noteworthy for a deliberate design choice on Expert difficulty. Designed by 譜面-100号 (Fumen -100 gou), the Expert chart contains a passage of unusually slow slide notes that forces players to refine their sense of slide timing, a section the community recognizes as an effective tutorial for intermediate players learning the slide mechanic. The Master chart, designed by ニャイン (Nyain), sits at level 12+ (constant 12.6) and is packed with 26 Break notes, making it a demanding play relative to its era. In maimai でらっくす Splash, Natural Flow received a refreshed jacket illustration, replacing the original artwork that had been used since the PLUS days.