Manga artist Nekotofu announced on Twitter that a TV anime adaptation of their work Onimai: I’m Now Your Sister! is in development. The anime’s official Twitter account posted an announcement PV and key visual to commemorate the start of the animation production. 

Voice actresses Marika Kouno and Kaori Ishihara will play siblings Mahiro Oyama and Mihari Oyama respectively. Their voices can be heard narrating the PV and introducing us to the manga’s story and characters. 

Nekotofu also posted a congratulatory message on their Twitter, noting that news of an anime adaptation coincides with Mihari Oyama’s birthday. 

本日はみはりちゃんのお誕生日です。プレゼントの中身はなんと…！？
『お兄ちゃんはおしまい！』突然のアニメ化決定！！
お陰様でついについに…！
順次情報が追加されるかと思いますので、アニメ公式を要チェック！
公式Twitter：@onimai_anime
公式サイト：https://t.co/Y6OBTABgI8#おにまい pic.twitter.com/xmZSOxoARk

— ねことうふ@おにまい (@nekotou) April 22, 2022

The anime series will be directed by Shingo Fujii (Mushoku Tensei: Jobless Reincarnation) and the screenplay will be written by Michiko Yokote (The Greatest Demon Lord Is Reborn as a Typical Nobody). Ryou Imamura (Kizumonogatari) is in charge of the series’ character designs. EGG FIRM is producing the adaptation while STUDIO BIND is handling the animation production. 

The original Onimai manga series was first published on June 27, 2018 in Ichijinsha’s Monthly Comic Rex magazine. Six tankoubon volumes of the series have been published as of April 21, 2022. 

Kodansha USA has published the series in English since August 31, 2021. They describe the story as: 

Mahiro Oyama was just a normal erotic-game loving dude…until he woke up one morning as a woman! Turns out his mad-scientist little sister, Mihari, tried out one of her new experiments on him…with a disastrous outcome, as far as Mahiro’s concerned! But Mihari is as determined to study him as he is determined to go back to his shut-in, game-playing life, and one thing’s for sure…life is going to get a whole lot weirder from here on out!

Source: Onimai Anime Twitter, Nekotofu Twitter Account