Words cannot describe how great this manga is as a trans person, and let's get this out of the way already: Yes, Mahiro IS transgender, and has had signs of being throughout the entire show, Mahiro herself is what we call in the community "An Egg", or, in other words, a trans person in denial, or a trans person that hasn't realized they're a trans person yet, which is where Mahiro falls in. Notice that never once Mahiro asks Mihari to turn her back into a boy, despite being in denial of her girlish qualities, some things she says feel like it's taken straight out of things said by trans people in denial on an Egg subreddit, and there's even more after what the anime is covering in the manga (Also, Mahiro is a great girl of culture, as she explicity says things against incest, pedophily and shipping real people), with out of the way, let's start.
Onii-chan wa Oshimai is a show that follows the struggles of a trans girl in denial to accept herself and become a sociable person, and it does that by showing Mahiro interact with different people, her change is displayed visually by how she slowly starts using different clothes inside home instead of the same oversized t-shirt and uses different hairstyles throughout the show, Mahiro turns out to be a super nice person, and the characters around her are fun to watch.
Visually, this show is breath taking, stunning animation and colors, nothing out of the ordinary for studio bind, huh? The pastel colors fit really well with the show and watching the characters move is hypnotizing, the animation is consistently great.
The music overall is your standard slice of life anime music but sometimes it throws a pretty dang good bgs on your face, sometimes there's soundchip songs and those are pretty good too
Overall, this is an anime for everyone, even taking into account the first episode and opening, which for some reason was much more sexualized than the following episodes (which almost disappears from the show by episode 4), as far as slice of lifes goes, this one is up there, and it's an incredibly wholesome show to watch