That Time I Got Reincarnated as a Slime tells the story of the salaryman turned slime hero, Rimuru Tempest, and his quest to build a new, tolerant nation of monsters where all can live freely. Rimuru is a selfless optimist and a good friend to all, and he has recruited many powerful beings to his side. But even he struggled to deal with the fiery Ifrit.
Early in the series, Rimuru met the masked hero, a powerful young woman named Shizue Izawa, who had come here from World War II-era Japan. She was a noble hero and a kind friend, but she was also Ifrit's host, and her time was running out. It fell to Rimuru Tempest to deal with the savage Ifrit, and figure out what to do with this loose end afterward.
When Rimuru & The Adventurers Faced Ifrit In Battle
Ifrit is a powerful fire spirit, and when Rimuru arrived in his new world, Ifrit was already living inside an unwilling host -- the masked hero, Shizue Izawa. When Demon Lord Leon Cromwell summoned Shizue as an Otherworlder from Japan, he placed Ifrit inside her, and at first, Shizue was in anguish. Ifrit was a powerful and terrifying monster, impossible to control, and Shizue cried out in horror when Ifrit killed the only friend Shizue had at the time. Shizue wasn't strong enough to defeat Cromwell and have Ifrit removed from her body, so she went her own way and became independent of Cromwell, aside from being Ifrit's unwilling vessel. That was when Shizue met and learned from the current masked Hero, and learned to tame the Ifrit spirit inside her.
From that point on, Shizue used her sword and Ifrit's fire powers to fight evil and monsters across the land, but she was losing control again, and by the time Rimuru met her during the main events of Reincarnated as a Slime, Ifrit was ready to break free. As Rimuru and Eren's friends watched, Ifrit took over Shizue's body and summoned its flames, and a battle began. Rimuru had to borrow Eren's ice magic to fight back against Ifrit's summoned clones, and then he used his Predator skill to absorb Ifrit directly. Even the proud, stubborn Ifrit was cowed when Veldora's own soul intimidated it, and Ifrit was tamed at last. Not long after that, Shizue shared some parting words with Rimuru and allowed him to absorb her. Now Ifrit was Rimuru's tool, not Shizue's, but he was even less willing to use it than Shizue had been.
The Minimal Role Of Ifrit In The Anime
Ifrit was safely and securely contained in Rimuru's body, putting an end to Ifrit's flaming rampage. This restored the peace, but Rimuru didn't have any immediate plans to use Ifrit's power as his own. In fact, he had absorbed Ifrit simply to get rid of it, a move to pacify the monster rather than harness it. Rimuru had plenty of other powers accumulated in his body already, and he saw little use for Ifrit's flames, so he merely acted as a living prison cell for Ifrit. For a time, Ifrit only made token appearances in the Reincarnated as a Slime anime, for comic relief. Ifrit had given up any hope of escape, so it settled down and started playing shogi matches with Veldora and commenting on Rimuru's daily life. Rimuru has a way of turning enemies into allies, or at least, taking the fighting spirit out of former enemies.
Ifrit made a token appearance during Rimuru's battle with Hinata Sakaguchi the knight commander when Rimuru borrowed Ifrit's power out of sheer desperation to deal with Hinata's overwhelming strength. Ifrit even appeared in bodily form during this battle, but it was for naught, and Rimuru withdrew Ifrit back into his body before moving on to other techniques. Even when Rimuru became a True Demon Lord, he still had limited use for Ifrit. When he gave Veldora a new humanoid body, Rimuru didn't give Ifrit its own body to match Veldora's.
Thus far in the anime, there is no sign that Ifrit will play a major role in Rimuru's quest, and it is mainly just a relic of a bygone era in Rimuru's journey. But there is still more story to tell, and it's plausible, even somewhat likely, that Ifrit will be reborn one day and become a new ally if Rimuru requires it. What is more, Ifrit represents the crime that Leon Cromwell committed to Shizue, and this is the source of Rimuru's simmering feud with Leon Cromwell. Now that they're both members of Octogram, Rimuru and Leon might come to blows over Leon's crimes and Ifrit's role in them. Ifrit may be imprisoned for now, but its impact on the world is still being felt.