Shizue Izawa (井沢静江 Izawa Shizue), was the companion of the previous Hero and a Japanese Summoned One.
She was also the mentor of several excellent pupils whom became important figures of society.
In her original world, she had no relatives and lived alone with her mother. Her father was drafted, and she couldn’t recall his face. Feeling neither blessed nor unfortunate, she had no choice but to accept it.
She was injured during the Bombing of Tokyo during World War 2. She was four at the time. Although she was summoned to this world during the bombing, it was not before she was badly burned. As she arrived, it was thus revealed that Demon Lord Leon Cromwell was responsible for saving her a whim. At first, he considered her existence a waste, a mere loss of a failed summoning attempt of Chloe. However, it was fate that Shizu gained a skill related to fire.
Surprised, Leon reconsidered her value to him and then called forth the Flame Giant Ifrit. He then had Ifrit possess Shizue's body, dashing her hopes for salvation. In truth, he did this to prevent the collapse of her body under the rampaging magic from the summoning. Thus, the pain she felt turned into hatred for Leon. As this curse engraved itself upon her heart, is can also be said that this possession enabled her to to stay alive.
As a flame demon, she ruled over one of the Demon Lord’s castle. By his side, as a high demon. When the hero invaded, Leon fled, abandoning his castle. She was left as the rear guard, a sacrificial pawn. The Demon Lord had treated her as a tool until the very end, nothing had indicated otherwise.
Ifrit knew it couldn’t win against the Hero before it, and when that thought overpowered Ifrit’s minds, a small fraction of the Shizue’s ego had returned. She looked the hero in the eyes. The hero then saved her. And from then on she was cared by the hero. She was given the Anti-Demon Mask to restrain Ifrit's control and cover her burn marks. Her whole body was covered with a robe, and thus she followed the hero. She was later known as the “Explosion Monarch.”
However, the Hero left on a journey one day. Although her reasons could not be understood, it was no doubt a reason the Hero could not ignore. The girl as well planned similar action. That one day she’d set of on a journey. To kill Demon Lord Leon Cromwell. Who had saved her life, and then threw her away. That is, killing Demon Lord Leon Cromwell became her life’s goal. Therefore, she hardly found the hero’s actions reproachable. But there was one regret left, she had never seen the hero’s smile. Since then, the girl became famous for her heroic deeds. and achievements.
Sometimes called one of the founders of the Freedom Association, she had worked for the expansion and benefit of the Adventurer Cooperation Union. She also took part training adventurers and her successors. At one time, she had taught two exceptionally excellent pupils, Yuuki Kagurazaka and Hinata Sakaguchi.
After the Adventurers Cooperation Union had formally changed its name to Freedom Association, Yuuki introduced the current ranking system. As a result of it, casualties during subjugation missions greatly decreased. Shizu began supporting Yuuki behind the scenes. That is, she no longer could do anything but guide new adventurers.
Later in the years, her time she spent as a demon have began to haunt her in her dreams. As her lifespan dwindled, she felt she was unable to restrain Ifrit’s consciousness any longer. However, the anti-demon mask had yet to fail her. Since she did not have much time left, she want to damage Leon before she dies. Thus, she decided to set off.
When she reported to Yuuki, without a word, he acknowledged her resolve. At the time, a message came from the Brumund Guild, about the investigation of Veldora’s disappearance by Cabal’s Party. In any case, they needed help to break into the forest. Someone needed to slip in with the trio. Their specialties she had heard from Yuuki. And as she had heard, they were a cheerful bunch. She was glad to have met such good companions on her last journey.
At the moment her life force finally ran out, Ifrit took over her consciousness. After Rimuru defeated Ifrit, Shizue’s consciousness returned. Her last request was for Rimuru to put her to rest within himself, and carry out her vengeance against Demon Lord Leon Cromwell.
Much later, during the duel between the new Demon Lord Rimuru Tempest and fully equipped Hinata Sakaguchi, fragments of what remained of Shizue's soul emerged from Rimuru's body with the help of Wisdom King Raphael. She spoke the last words she had for Hinata, removing the curse of "Though Manipulation" from Hinata's mind and parted with warning for Hinata to be cautious of Kagurazaka Yuuki.