Monster features a loose fighting system like other anime fighting games, but with a somewhat slower, more deliberate pace. It also features a Street Fighter Alpha 3 groove-style "shift" system, which allows the player to select one of three different modes to customize gameplay - Monster, Freedom, and Tranquility. Monster reduces attack speed but increases damage for a tankier gameplay style; freedom reduces damage and allows moves to be cancelled into each other for rushdown-oriented play; and tranquility emphasizes defense and improves moves' invincibility properties. When activated, these modes also change other special move properties to allow for further flexibility in gameplay styles.
An arcade sequel was announced in 2008, to be published by Examu. It was quietly cancelled after location tests over a few years.
This version of the game is a CD released at Comiket. It contains the 1.0 release. The final release was version 1.11B; the included update_mnstprd_111b.exe file will update the game to that version.