In Tempest, preparations were underway for a banquet before Rimuru's return. But then came Myurran, a demon sent to infiltrate Tempest as a sentinel for Demon Lord Clayman. She accompanies Youm's group as a military advisor, and upon entering Tempest, she is surprised by the power of the country, and deepens her relationship with the inhabitants. At the same time, King Edmaris of the Kingdom of Falmuth, who finds Tempest an eyesore, colludes with the Holy Church of the West and plans to invade Tempest.

As Tempest is attacked, an assailant appears in front of Rimuru. It is Shizu's other student, the strongest Holy Knight, Hinata Sakaguchi.