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Eir Aoi Chosen to Perform New Opening of That Time I Got Reincarnated as a Slime Season 4

By Josh Piedra Posted: March 9, 2026 7:07 AM EDT

Slime Azure Sea | The Outerhaven

Eir Aoi’s new song “Unrealistic” has been selected as the opening theme for That Time I Got Reincarnated as a Slime Season 4.

“Unrealistic” is an intense rock number built around a full band sound that matches the epic scale of the Tensura story. Be sure to check out Eir Aoi’s evolving sound as she begins a new chapter with Lantis.

A CD featuring “Unrealistic” is set for release on April 22, 2026. This CD will also include “MONSTER,” the opening theme for Classroom of the Elite 4th Season: Second Year, First Semester, making it a double tie-in single.

Eir Aoi commented on the song:

When I learned that I would be performing the opening theme for That Time I Got Reincarnated as a Slime, a series loved by fans all over the world, I was truly surprised. More than anything, I couldn’t contain my excitement.

“Unrealistic” is an intense rock number that matches the epic scale of the story. I hope you’ll enjoy it together with the anime.

Source: Press Release

anime That Time I Got Reincarnated as a Slime Eir Aoi

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Josh Piedra

Josh has been an anime fan for nearly twenty years. In addition, he is a light novel author with over 25 books published as well as the owner of Meteora Press, his personal publishing label. Anime and otaku culture isn't Josh's only area of expertise. He also has a Bachelor of Arts in Game Design and has created a handful of independent games along with a deep working knowledge of the gaming industry.

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