"Myth of Fantasy" is a well-known online game. When the 12th expansion pack was updated, an accident trapped 30,000 players in the virtual world constructed by the game. The veteran player Shiroe (voiced by Takuma Terashima) is one of them. Although he is introverted in real life, he is extremely capable of leadership in the game and is trusted and loved by his companions. Fear and despair loom over the heads of the players trapped in the game. The cheerful and straightforward warrior Naotsugu (voiced by Tomoaki Maeno), the assassin Akatsuki with a cute appearance and strong strength (voiced by Emiri Kato), and Shiroe stood up and founded the union "Log Horizon". They set out from the metropolis Akihabara and embarked on an adventurous journey, determined to open up their own world and find a way out.