ChaOS TCG, officially titled Character Operating System (ChaOS), is a collectible card game published by Bushiroad in Japan starting in February 2009. The game is structurally similar to Bushiroad's better-known Weis Schwarz system: players build decks around licensed anime and visual novel franchises, with each franchise designated as an 'OS.' Cards from different OS sets are compatible within the same game system, allowing players to mix characters across intellectual properties. Licensed sets include titles such as Nitroplus visual novels, Shin Koihime Muso, and later entries such as Danganronpa: The Animation (2013) and Overlord (2018). Each new OS launched with a Trial Deck and accompanying booster packs. Although the game reached overseas collector markets through import retailers, it was never officially localized into English. Bushiroad discontinued the line as its Weis Schwarz and Cardfight Vanguard platforms expanded, leaving ChaOS TCG as a notable artifact of early 2010s anime card game proliferation in Japan.
Source: boardgamegeek.com/boardgame/316184/chaos-trading-card-game