That Time I Got Reincarnated as a Slime: Shizue Izawa

She's an Summon who survived the events of World War II in the real world when she was 4, she was brought in the isekai world by the demon king, Leon Cromwell, and made her the vessel of the fire spirit Ifrit due to her being an failed Summon, soon afterwards, she earned the title, "Conqueror of Flames" due to her fire-type attacks and defenses. She is one of the founders of the Freedom Association, she had worked for the expansion and benefit of the Adventurer Cooperation Union and she also took part training adventurers and her successors. Later, she suffered from nightmares of Leon and Ifrit, and felt that she was unable to restrain Ifrit's consciousness any longer even with her anti-demon mask, causing her to age rapidly and her goal was to defeat Leon from tossing her aside after he saved her despite her life was at its end.