ONIMAI: I'm Now Your Sister!

Alt title: Onii-chan wa Oshimai!

TV (12 eps)
3.794 out of 5 from 1,679 votes
Rank #2,261

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: Kodansha

my anime:

User Stats

4,788 users are tracking this. to see stats.

If you like this anime, you might like...



EnglishAaaaah… I don’t know what to think of this series… It does come from a good place : revealing to a masculine audience some realities of a girl’s life which they probably aren’t aware of, like having periods or taking care of long hair. Even though on that last point, the anime clearly goes overboard, you don’t actually need all that… :’-)But intention isn’t all and I still feel uneasy regarding the fact that, just by having a female body, the protagonist is suddenly inclined towards “girly” tastes, like shopping, eating sweets, cooking or yaoi. And on the other hand, the anime purposefully avoids less tasty aspects of a girl’s life in Japan, like getting molested in public transport or the ubiquitous misogyny.Finally, without spoiling, the last episode offered an opportunity to say some things which would have made the character’s relationships healthier, but the characters involved deliberately chose not to say these things, which made the situation go from awkward to downright immoral.The drawing are cute and the boobs look good, and the music does the job.FrançaisAaaaah… Je ne sais pas quoi penser de cette série… Dans le fond, ça part d’un bon sentiment : faire découvrir à un public masculin certaines réalités de la vie des filles dont ils n’ont sans doute pas conscience, comme avoir ses règles ou entretenir des cheveux longs. Même si sur ce dernier point, l’animé abuse clairement, y’a pas besoin de tout ça… :’-)Mais l’intention ne fait pas tout, et je reste mal à l’aise vis-à-vis du fait que, du simple fait d’avoir un corps de fille, le protagoniste se met à avoir des goûts et des intérêts « de fille », comme faire du shopping, manger des trucs sucrés, faire la cuisine ou le yaoi. Et a contrario, l’animé se garde bien d’aborder les aspects moins glamour de la vie d’une fille au Japon, comme se faire tripoter dans les transports ou la misogynie ambiante.Enfin, sans divulgâcher, le dernier épisode offrait l’opportunité de dire certaines choses qui auraient assaini les relations entre les personnages, mais les personnages impliqués ont délibérément fait le choix de ne pas dire ces choses, ce qui fait basculer la situation du gênant à l’immoral.Les dessins sont mignons et les nichons bien dessinés, et la musique fait l’affaire.


The series does start with premise of sister turning her older brother into a girl by made up drug in order to reform his life. How would that ever work? I’m asking myself the same question. After one or two episodes this idea is put aside for slice-of-life with bunch of girls … including Mahiro the older brother, who is now a middle school girl [1]. Gender bender element resurfaces occasionally throughout the series. It is not the type, where the main character goes back and forth between having female body and male body a lot [2]. Slice-of-life aside it has some wholesome moments and it has some yuri and plentiful of other fanservice tease in it. I did watch the uncensored version. It has comical moments too. It doesn’t have much of overarching story to speak of only the relationships between the characters. I like how it shows Mahiro and his sister Mihari deep down care for each other. Other central characters are Mihari’s friend Kaede and her younger sister Momiji plus friends/classmates of the sister, which are introduced bit later on. Each has different role in the group’s dynamic. Visually the series looks good. What I like very much is voice acting - Japanese dub. Music and soundtrack worked for me quite well. OP and ED is decent. Overall, an enjoyable slice-of-life it does have the gender bender twist, but more than that it’s about having friends and good relations with siblings. Spoilers [1] Yes, he does enter a middle school. [2] It happens only once partially in the last episode.

See all reviews

Related manga


See all characters


See all staff


Custom lists

See all custom lists