《明日方舟》同人游戏，以原作角色“老鲤”为主角，在二十年前的龙门，展开一系列解谜探案故事。
Zhang Xiao, a senior high school student, has a strange power called “Master Key”. Since he was young, he can communicate with other “worlds”. One day, Zhang Xiao’s classmate Miao Xueling had an accident.