One day, in the midst of the improvements on the Goblin Village with the help of Kaijin and the dwarves, Rimuru meets a trio of adventurers from the Guild who've been temporarily joined by a masked woman named Shizu. Shizu turns out to be the person Rimuru is destined to be with, as his fortune said. Shizu also came to this world from Japan, but unlike him, she was summoned here many years ago. So Rimuru uses his Thought Communication skill to show Shizu what Japan looks like today.

The Demon Lord Leon Cromwell summoned Shizu out of Tokyo as it burned during in the air raids, then forced the high-ranked spirit Ifrit to possess her. After taking over Shizu's body, Ifrit begins to rampage.

When Shizu was still with Demon Lord Leon, it was a Hero who rescued her. That Hero was Shizu's inspiration to help as many people as she could for many years. She even worked as a teacher for children who'd come from other worlds. And now, as her time comes to an end, Shizu asks Rimuru for one last favor...

The threat of Charybdis has gone. That night, Rimuru has a dream in which he sees Shizu teaching children at her school in the Kingdom of Ingrassia—a dream showing Shizu's lingering regret. To see her wishes through, Rimuru leaves the Jura Tempest Federation and heads for the capital of the Kingdom of Ingrassia. His first goal is to meet with the Grandmaster of the Guild, Yuuki Kagurazaka, who happens to be a Summon and a former student of Shizu's.

Rimuru and the children reach the deepest level of the Dwelling of Spirits, where they stand on a pedestal bathed in light to summon superior spirits. Will their summoning be successful? Amidst the uncertainty, the first to attempt the summoning is Gale, followed by Alice, Kenya, Ryota, and finally Chloe. But instead of a spirit, Chloe's summoning brings forth an unknown spiritual form with an immense amount of energy. Just what is this spiritual being? Ramiris seems to sense something about it...

This story takes place before Rimuru's reincarnation. Shizu, also known as the Conqueror of Flames, responds to an urgent request calling her to the Kingdom of Filtwood. When she reaches the castle, many adventurers are already there. What request could have demanded such a huge gathering? It turns out a demon has been revived, and the adventurers have been called to subjugate it. It is said that more than ten of the most skilled adventurers have already been killed by this demon. But there is more to this request than meets the eye...

A merchant from the east brings Hinata Sakaguchi a new book. In it she finds surprising information about the Jura Tempest Federation, a nation of monsters. As a former student of Shizu's, what goes through Hinata's mind upon learning about the existence of Rimuru? This special episode gives some hints as to what's coming in the new arc, as well as a look back at Rimuru's exploits thus far.

At the same time as the attack on Tempest, Rimuru is also under attack. With one look, Rimuru realizes that his assailant is one of Shizu's former students, an Otherworlder, and the woman then introduces herself as the strongest of the Holy Knights, Hinata Sakaguchi. Rimuru is backed into a corner when her Holy Field seals most of his magic. At the same time, Shion and Hakurou, whose magic has been sealed by a similar barrier, are backed into a corner by Shogo and Kyoya.