Oniichan wa Oshimai!
English name: Onimai: I'm Now Your Sister!
Genres: Comedy
Type: TV, Episodes: 12
Aired: Jan 5, 2023 to Mar 23, 2023
Studio: Studio Bind
Source: Manga
Rating: PG-13 - Teens 13 or older
Synopsis:
Self-professed "home security guard" Mahiro Oyama has not left his home in years, secluding himself in his room playing erotic visual novels. This depraved lifestyle causes his prodigious sister, Mihari, to worry about his well-being. In hopes of solving this problem, she devises a plan to rehabilitate him back to normalcy.

The first part of Mihari's plan is to concoct a medicine that changes her brother's biological constitution into a bona fide female, much to Mahiro's vehement dismay. Stuck in this predicament, Mahiro has no choice but to live out his life as a cute girl until the effect wears off—if it ever does.