The tale begins with the hero's party reaching the Demon King’s castle, determined to defeat him. Instead, they are stopped by Yoki, a demon so powerful that all their efforts to fight him end in failure. Yoki easily shatters fireballs, dodges attacks, and even withstands holy sword strikes, leaving the party defeated. Strangely, instead of killing them, Yoki orders his subordinates to take them to the nearest village. For a month, the hero's party continues challenging Yoki—thirteen attempts in total—but they never prevail. Yoki’s mysterious reasons for sparing them perplex even the Demon King himself.