ONIMAI: I'm Now Your Sister!

ONIMAI: I'm Now Your Sister!

Onii-chan wa Oshimai!

OngoingComedySlice of Life

by Nekotoufu0views

No ratings

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! *5th place of Tsugi Manga Awards, Category Webmanga - **Retail:** (Direct Retail From the Mangaka) ![](https://i.imgur.com/0e9KPgq.png) [Official Melon Books](https://www.melonbooks.co.jp/circle/index.php?circle_id=3753) ![](https://i.imgur.com/t9hf4kQ.png) [Official Toranoana](https://ec.toranoana.shop/tora/ec/cot/circle/2UPA116P847KdC6Rd687/all/) ![](https://i.imgur.com/lGJEbPa.png) [Official DLSite](https://www.dlsite.com/home/circle/profile/=/maker_id/RG40614.html) (jp)

First chapter Latest chapter

Chapters209

Ch. 111Mahiro and the Fun-filled Lion's Den

Ch. 110Mahiro and the Demon of the Prefect Council

Ch. 109Mahiro and a Healthy Beauty Regimen

Ch. 108.5 A DATE WITH NEMU

Ch. 108Mahiro and Bodyguards

Ch. 107.9Minato-kun is Done For? 3

Ch. 107.5MAHIRO AND THE MAKEOVER

Ch. 107Mahiro and Popularity Rankings

Ch. 106Mahiro and Sharing Secrets

Ch. 105Mahiro and an Offline Adventure

Ch. 104.5MAHIRO AND THE MOTHERLY EMBRACE

Ch. 104Mahiro and Mother's Day

Ch. 103Mahiro and Heaven or Hell

Ch. 102.2Aoi-chan Edition

Ch. 102.1Niichi-chan Edition

Ch. 102Mahiro and a Technological Nightmare

Ch. 101.5MAHIRO AND THE FEMALE CHARACTERS

Ch. 101Mahiro and a Celebration

Ch. 100.9Onii-chan's Drawing Book

Ch. 100Mahiro and a Good Day for an Experiment

Ch. 99.5Mahiro and Getting a License + Doujin Issue 33 Extras

Ch. 99Mahiro and the Autobahn

Ch. 98.5Mahiro and Being a Small Fry Human

Ch. 98Mahiro and a One-Night Stay

Ch. 97Mahiro and Crossing the Line

Ch. 96Mahiro and a Token of Appreciation

Ch. 95.9Minato-kun is Done For? 2

Ch. 95.5Miyo and the Date

Ch. 95Mahiro and the University Expedition Squad

Ch. 94Mahiro and the New School Year, Once Again

Ch. 93.5The Boys and Another Shot

Ch. 93Mahiro and a Special Treat

Ch. 92.5Asahi and Growth

Ch. 92Mahiro and a Maiden's Secret

Ch. 91.5Nemu and Nodoka

Ch. 91Mahiro and Marriage

Ch. 90.9Volume 9 Special Edition Extras

Ch. 90.8Mahiro and Mama (Revisited)

Ch. 90.5Chapter 90.5

Ch. 90Mahiro and Celebrating Success

Ch. 89Mahiro and a Home Visit

Ch. 88.5Chapter 88.5

Ch. 88Mahiro and Romantic Antics

Ch. 87Mahiro and Special Techniques

Ch. 86.9Minato-kun is Done For? 1.5

Ch. 86.5Special: Asahi's Birthday

Ch. 86Mahiro and Overflowing Maternal Instincts

Ch. 85.5Chapter 85.5

Ch. 85Mahiro and a Stressful Reunion (Part 2)

Ch. 84Mahiro and a Stressful Reunion (Part 1)

Ch. 83.9Minato-kun is Done For? (Full Version)

Ch. 83Mahiro and the New Year's Tour

Ch. 82.5Chapter 82.5

Ch. 82Mahiro and a Silent Night

Ch. 81.9Minato-kun is Done For? (Preview Version)

Ch. 81.8Non-Mahiro Special: Aoi-chan Edition

Ch. 81.5Chapter 81.5

Ch. 81Mahiro and Conflicting Views

Ch. 80.8Mahiro and the Growing Gal Gang + Volume 8 Extras

Ch. 80Mahiro and the Secret Engagement

Ch. 79Mahiro and the Gal Gang

Ch. 78.9Mihari's Research Lab

Ch. 78.5The Boys and MMORPGs

Ch. 78Mahiro and MMORPGs Revisited

Ch. 77Mahiro and the Farewell Party

Ch. 76.9The Research Lab's Mihari-chan

Ch. 76.1Blu-Ray Box Volume 2 Add-in Comic

Ch. 76Mahiro and a Close Call

Ch. 75Mahiro and the Siren's Call

Ch. 74.99Mihari's Birthday Venue

Ch. 74.5Everyone and the Blackout

Ch. 74.1Blu-Ray Box Volume 1 Add-in Comic

Ch. 74Mahiro and a Night Together

Ch. 73.5Non-Mahiro Special: Nii-chan Edition

Ch. 73.1Mahiro-chan's Birthday Venue (2023)

Ch. 73Mahiro and Big Bro's Secrets

Ch. 72.9The Boys Are Done For Too! + Omnibus 22-23-24 Extras

Ch. 72Mahiro and an Admiration

Ch. 71.5Mahiro and the Magazine Model

Ch. 71Mahiro and the selfie boom

Ch. 70.9Volume 7 Special Booklet

Ch. 70.8Volume 7 Extras

Ch. 70.7Mahiro and a Discussion on Cosplay

Ch. 70Mahiro and an autumn outing

Ch. 69.99Nayutan's Birthday Venue

Ch. 69.5Mahiro and a Moment of Glory

Ch. 69Mahiro and the Youthful Sports Festival

Ch. 68.99Momiji Birthday Venue

Ch. 68Mahiro and the World of Hobbies

Ch. 67.99Kaede-chan's birthday venue

Ch. 67Mahiro and Male Pride

Ch. 66.5The Boys and Changing Shifts

Ch. 66Mahiro and the Tempting Culture Festival (Part 2)

Ch. 65Mahiro and the Tempting Culture Festival (Part 1)

Ch. 64Mahiro and a Healthy Diet

Ch. 63.99Omnibus 19-20-21 Extras

Ch. 63.5Momiji and Panties

Ch. 63Mahiro and Staying Over Because of Rain

Ch. 62.5Nemu and Summer Vacation

Ch. 62.1Mihari-chan's Birthday Venue

Ch. 62Mahiro and a 2nd Semester Debut

Ch. 61Mahiro and Summer Festival

Ch. 60Mahiro and Summer Homework

Ch. 59Mahiro and spring cleaning

Ch. 58Mahiro and the Marine Ranger (Part 2)

Ch. 57Mahiro and the Marine Ranger (Part 1)

Ch. 56Mahiro and The Battle Plan Meeting

Ch. 55Mahiro and a Summer Adventure

Ch. 54.9Omnibus 16-17-18 Extras

Ch. 54.7Mahiro and Harems

Ch. 54.5Mahiro and the serene mind

Ch. 54Mahiro and School Ghost Stories

Ch. 53.5Boys and Girls

Ch. 53Mahiro and the North Wind and Sun

Ch. 52Mahiro and the Little Garden

Ch. 51Mahiro and Passing the Rainy Season

Ch. 50.5Chapter 50.5

Ch. 50Mahiro and Swim Classes (Part 2)

Ch. 49Mahiro and Swim Classes (Part 1)

Ch. 48.5MAHIRO AND THE PARENT-TEACHER CONFERENCE

Ch. 48Mahiro and Class Observation

Ch. 47Mahiro and the Sunny Girl

Ch. 46.5Mihari and Memories of Stickers

Ch. 46Mahiro and Sticker Collecting (fixed)

Ch. 45.9Omnibus 13-14-15 Extras

Ch. 45.7Mahiro and Visible Undergarments

Ch. 45Mahiro and the Season for New Clothes

Ch. 44Mahiro and the Secret BBQ

Ch. 43.5Chapter 43.5

Ch. 43Mahiro and Fragrances

Ch. 42.6EX3 Special - Mahiro and a Hair's Breadth from Danger!

Ch. 42.5[TEMP 1]41.3+41.7 & 42.5 & Mini Extra (2 of 10)

Ch. 42Mahiro and the Gift of Memories

Ch. 41Mahiro and the Physical Examination

Ch. 40.99Bonus Illustration

Ch. 40.8Mihari and Skipping Grades

Ch. 40.6Mini Extras [Complete]

Ch. 40.5Mahiro and Barefoot

Ch. 40Mahiro and an Important Secret (Part 2)

Ch. 39Mahiro and an Important Secret

Ch. 38.5Momiji and Massages

Ch. 38Mahiro and an Appreciated Break

Ch. 37.5Mihari and High School Girls

Ch. 37Mahiro and a Girl's Mannerisms

Ch. 36.9Mahiro's Weekday Routine + Omnibus 10-11-12 Extras

Ch. 36.5Mahiro and a Present

Ch. 36Mahiro and a Surprise

Ch. 35.6EX2 Special - I am Mahiro and I am Mihari

Ch. 35Mahiro and the Guidance of Fortunes

Ch. 34.5Chapter 34.5 (1+2+3)

Ch. 34Mahiro and the Adult's Door

Ch. 33.5Mahiro and Handmade

Ch. 33Mahiro and Valentine's

Ch. 32.5Mahiro and Drinks

Ch. 32Mahiro and a Surprise Visit

Ch. 31Mahiro and Charming Bare Legs

Ch. 30.9Chapter 21-30 Mini Extras [Complete]

Ch. 30.8Asahi and Momiji

Ch. 30.5Mahiro and Hot Kiss

Ch. 30Mahiro and the Coming and Going Year

Ch. 29Mahiro and a Double Date

Ch. 28.1Mahiro and Girl's Night (Second Part) [Tank Version]

Ch. 28Mahiro and Girl's Night (Second Part) [Pixiv Version]

Ch. 27.99Omnibus 7-8-9 Extras

Ch. 27.5Including Extra (25.5 - 26.5 - 27.5)

Ch. 27Mahiro and Girl's Night (First Part)

Ch. 26Mahiro and Patissier

Ch. 25Mahiro and Finals

Ch. 24.5Part 1: Mahiro and Bento & Part 2: Mihari and Bento

Ch. 24Mahiro and Common Interests

Ch. 23Mahiro and the Fun Weekend

Ch. 22.5EX Special - Mahiro and an Uneventful Holiday

Ch. 22Mahiro and the Harsh Lesson

Ch. 21Mahiro and the First Day of School (V2)

Ch. 20.9Chapter 11-20 Mini Extras

Ch. 20.5Mihari and Dresses + Mihari (afterwards) and Dresses

Ch. 20Mahiro and Middle Schoolers (v2)

Ch. 19Mahiro and Uploading Videos

Ch. 18.99Omnibus 4-5-6 Extras

Ch. 18.5Part 1: Mahiro and a "Comrade's" Return & Part 2: Mahiro and Perms

Ch. 18Mahiro and the Onsen Panic (Second Part)

Ch. 17Mahiro and the Onsen Panic (First Part)

Ch. 16Mahiro and the Hair Salon

Ch. 15.5Siblings and Kotatsu

Ch. 15Mahiro and Party Night

Ch. 14Mahiro and a Little Adventure

Ch. 13Mahiro and a Wholesome Relationship

Ch. 12.5Mahiro and Nichiasa

Ch. 12Mahiro and a Lonely Night

Ch. 11Mahiro and Adventure

Ch. 10.99Omnibus 1-2-3 Extras

Ch. 10.9Chapter 1-10 Mini Extras

Ch. 10.5Mahiro and Helping Out & OMAKE - Mihari and Onii-chan

Ch. 10Mahiro and Special Home Security

Ch. 9.5Mahiro and the Two's Secret

Ch. 9Mahiro and a Girl's Vacation

Ch. 8.5Mahiro and Gacha (v2)

Ch. 8Mahiro and New Game

Ch. 7Mahiro and Encounters with the Unknown

Ch. 6.5Mahiro and Going in Circles

Ch. 6Mahiro and the Secret Garden

Ch. 5.5Mahiro and Comfort for Many Days

Ch. 5Mahiro and a Melancholic Day

Ch. 4Mahiro and MMORPG

Ch. 3Mahiro and Identity

Ch. 2Mahiro and the Dangerous Mirror

Ch. 1.5Mahiro and the Toilet

Ch. 1Mahiro and the Unpleasurable Body

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