Emil Chronicle Online was a 3D Japanese fantasy MMORPG with anime-style graphics. Set in the land of Acronia, the game featured twelve classes spread among four races, each with a particular advantage (agility, magic, or strength). Along with a series of quests and battles, the game featured a few standout modes including its marionette system, where players could transform their characters into marionettes, which were Pokémon-like surrogates. Marionettes could live in the world even when players had logged out. There was also a standard pet system outside of this. Players could also turn their characters into weapons that other people could use, gaining both experience. PvP was in RvR format, and massive battles were scheduled regularly in advance for different level groups. As of 2024, no servers for the game are online, with GungHo Online Entertainment announcing that the Japanese server would be shut down on August 31, 2017, citing the impossible task of keeping up with modern players’ demands.

The world of Emil Chronicle Online is divided into three realms, homelands of each of the three original races: the humans or Emils, the angel-like Titanias and the demon-like Dominions. In relation to our understanding of the worlds Titania is above the world of Emil, while Dominion is below it. The main stage is set in the land of Acronia, situated in the Emils' world, with the city of Acropolis at its centre. In the distant future, civilization completely depleted the earth's valuable resources. In its search for new resources, worlds which were never meant to be connected were bridged. Complete chaos ensued between the three races. Humans entered into the heavens and underworlds, realms never meant for them. From the aftermath of chaos was the emergence of a new history. There was a great effort to rebuild and regroup as each race reclaimed their rightful spot in the world.