I Got a Cheat Skill in Another World and Became Unrivaled in the Real World, Too

I Got a Cheat Skill in Another World and Became Unrivaled in the Real World, Too, (異世界でチートを手にした俺は、現実世界をも無双する〜レベルアップは人生を変えた〜) shortened to Iseleve (いせれべ), is a Japanese light novel series written by Miku and illustrated by Rein Kuwashima. It began as a web novel that started in the Kakuyomu website in March 2017. It was later acquired by Fujimi Shobo, who have published the series since December 2018 under their Fujimi Fantasia Bunko imprint.

A manga adaptation illustrated by Kazuomi Minatogawa has been serialized on ASCII Media Works' Dengeki PlayStation Comic Web website since December 2019, with its chapters collected into five tankōbon volumes as of August 2023. An anime television series adaptation produced by TMS Entertainment and animated by Millepensee aired from April to June 2023. A new anime project has been announced.

Plot
Yūya Tenjo is an overweight, short and meek middle school student who is bullied at school and tormented by his family, except for his grandfather who is the only person who cares for him. When his grandfather dies and leaves Yūya as the sole heir of his house, his parents expel him from home, and he is forced to live there alone. Inside his grandfather's house, Yūya discovers a portal to another world named Argena, where he obtains power that will change his life forever as it leads him into battle against multiple powerful malevolent entities, demons, extraterrestials, and even gods, sometimes for the sake of the very fabric of existence itself.

Light novel
Written by Miku, the series began publication online in the Kakuyomu website on March 25, 2017, under the tentative title Level Up wa Jinsei o Kaeta (レベルアップは人生を変えた). The series was later acquired by Fujimi Shobo, who began publishing the novels with illustrations by Rein Kuwashima starting on December 20, 2018, under their Fujimi Fantasia Bunko imprint. As of July 2024, sixteen volumes have been released.

In September 2021, Yen Press announced that they had licensed the novels for English publication.

A spin-off series titled I Got a Cheat Skill in Another World and Became Unrivaled in the Real World, Too: Girls Side (異世界でチート能力を手にした俺は、現実世界をも無双する　ガールズサイド ～華麗なる乙女たちの冒険は世界を変えた～), written by Ryō Kotohira and illustrated by Kuwashima, began publication under the Fantasia Bunko imprint on December 20, 2022. As of May 2024, five volumes have been released. Its plot deals with Princess Lexia's impulsive decision to engage in a "learning journey" throughout her world in order to become Yūya's equal, and ends up gathering her own experiences to help her grow into her own.

Manga
A manga adaptation illustrated by Kazuomi Minatogawa began serialization on ASCII Media Works' Dengeki PlayStation Comic Web website on December 13, 2019. As of August 2023, five tankōbon volumes have been released. Yen Press has also licensed the manga in English.

A manga adaptation of the spin-off series Girls Side, illustrated by Miinosuke Seo, began serialization on the KadoComi and Nico Nico Manga websites on April 25, 2024.

Anime
In August 2022, it was announced the novels would be receiving an anime television series adaptation. The series is produced by TMS Entertainment and animated by Millepensee, with Shingo Tanabe directing, Shin Itagaki serving as chief director and supervising the scripts, Hiromi Kimura adapting Rein Kuwashima's character designs for animation and serving as chief animation director, and Akiyuki Tateyama composing the music. It aired from April 7 to June 30, 2023, on Tokyo MX and other networks. The opening theme song is "Gyakuten Geki" (逆転劇) by Tsukuyomi, while the ending theme song is "Hachimitsu" (ハチミツ) by Shikao Suga. Crunchyroll licensed the series, and will be streaming it along with an English dub. Muse Communication licensed the series in Asia-Pacific. The initial streaming of the series' 13th and final episode was inexplicably delayed by two days, which ended up airing on June 28, instead of June 26.

A new anime project was announced during the "Fantasia Bunko Daikanshasai Online 2023" livestream on October 14, 2023.

Game
A free-to-play MMORPG browser game, titled I Got a Cheat Skill in Another World and Became Unrivaled in the Real World Too: Parallel Universe, was announced on March 17, 2023. It will be launched on the G123 platform in multiple languages.

Reception
In May 2018, the web novel won the Grand Prize at the 3rd Kakuyomu Web Novel Contest in the Science Fiction/Modern Fantasy Division. By October 2023, the series had 3 million copies in circulation.