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This wiki is based off the manga/anime series Onimai: I'm Now Your Sister! also known as Onii-chan wa Oshimai!

This wiki was founded on January 7, 2023. We currently have 455 articles, 692 images, and 9,609 edits.

At present, the Wiki only covers material and characters from the first eight volumes (as only those seven volumes have been published in English), but more is intended to be added in the future once additional chapters are published in North America with official English Translations.

We use a formal style on this wiki, with an in-universe style of description. Please use existing infoboxes, and be sure to create redirects for chapters, characters, and episodes. Note that we are a fan-based wiki, and we cover only official content from the franchise.

If there are any questions, get in touch with the wiki's admins. Other than that, happy editing.

We're a collaborative community website about Onii-chan wa Oshimai! that anyone, including you, can build and expand. Wikis like this one depend on readers getting involved and adding content. Click the "ADD NEW PAGE" or "EDIT" button at the top of any page to get started!

Introduction

The series follows Mahiro Oyama, an otaku living with his scientist younger sister Mihari. One day he wakes up as a young girl, a result of one of Mihari's experiments. Mahiro must now learn to live as a middle school girl, all while making friends in his new school.

Characters

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Chapters
Main Chapters		1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 • 26 • 27 • 28 • 29 • 30 • 31 • 32 • 33 • 34 • 35 • 36 • 37 • 38 • 39 • 40 • 41 • 42 • 43 • 44 • 45 • 46 • 47 • 48 • 49 • 50 • 51 • 52 • 53 • 54 • 55 • 56 • 57 • 58 • 59 • 60 • 61 • 62 • 63 • 64 • 65 • 66 • 67 • 68 • 69 • 70 • 71 • 72 • 73 • 74 • 75 • 76 • 77 • 78 • 79 • 80 • 81 • 82 • 83 • 84 • 85 • 86 • 87 • 88 • 89 • 90 • 91 • 92
0.1 - 0.9 Chapters		1.25 • 1.5 • 5.5 • 6.5 • 8.5 • 9.5 • 10.5 • 12.5 • 15.5 • 18.5① • 18.5② • 18.75 • 21.5① • 21.5② • 21.5③ • 21.5④ • 24.5① • 24.5② • 25.5 • 26.5 • 27.5 • 30.5 • 32.5 • 33.5 • 34.5① • 34.5② • 34.5③ • 36.5 • 37.5 • 38.5 • 40.5 • 41.3 • 41.7 • 42.5 • 43.5 • 46.5 • 47.5 • 48.5 • 50.5 • 51.5 • 53.5 • 54.5 • 56.5① • 56.5② • 58.5 • 62.5 • 63.5 • 66.5 • 69.5 • 71.5 • 74.5 • 78.5 • 81.5 • 82.5 • 85.5 • 88.5 • 90.5
Collected Works Special Chapters		Real Record! Drama CD Report • Mahiro and the After-Travel Party • Mahiro and a Sleepy Day • Mahiro's Weekday Routine • Mahiro and the Visible Undergarmets • 2020 Summer Special Brochure • Mahiro and the Harem • Mahiro and After the Festival • The Boys Are Done For!
Tankōbon Bonus Chapters		Mihari and Her Onii-Chan • Mihari's Wardrobe • Mihari's Wardrobe Afterwards • Miyo's Refusal • Asahi's Innocence • Momiji's Nickname • Kaede's Concern • Mahiro's Lunch • Mihari's Lunch • Asahi and Momiji • Mihari's Skipped Grades • Nayuta's Recent Past • Mahiro and the Photo Albums • Mahiro's Cosplay Round-Table • Mahiro and the Ko-Gal Squad • TBA
Tankōbon Special Chapters		Mahiro's Colorful Life • Mahiro's Anime Time • Miyo and the Enchanted Night • Asahi and Nii-chan • Perfect Onee-chan • Mihari's Research Lab • TBA
EX Special Chapters		Mahiro and the Uneventful Holiday • Later in the Lab • Mahiro is Me and Mihari is Me • Mahiro in a Close Call
Spin-off Special Chapters		A Story Where That Grows • Mihari and the Drinking Party • A Story Where That Grows Part 2 • Minato-kun is Done For? • Offline Meeting Night • Minato-kun is Done For? 1.5
Blu-ray Special Appendix Chapters		Blu-ray Volume 1 Appendix Manga • Blu-ray Volume 2 Appendix Manga
Anthology Chapters		1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 • 26 • 27 • 28 • 29 • 30 • 31 • 32 • 33 • 34 • 35 • 36 • 37 • 38 • 39 • 40 • 41 • 42 • 43 • 44 • 45 • 46 • 47 • 48 • 49 • 50 • 51 • 52 • 53 • 54 • 55 • 56 • 57 • 58 • 59 • 60 • 61 • 62 • 63 • 64 • 65 • 66 • 67 • 68 • 69 • 70 • 71 • 72 • 73 • 74 • 75 • 76
Idol Stuff		1 • 2
Niwasaki Diary		1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11

Manga
Doujinshi		1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 • 26 • 27 • 28 • 29 • 30
Collected Works		1 • 2 • 3 • 4 • 5 • 6 • 7 • 8
Tankōbon		1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9
EX Specials		EX Special • EX2 Special • EX3 Special
Spin-off Doujinshi		Good Night Onii-chan! • Mihari-chan in the Laboratory • Onimai Side Reader: Mihari's Laboratory • Minato-kun is Done For? • Minato-kun is Done For? 1.5
Anthology		1 • 2 • 3 • 4 • 5
Drama CDs		Drama CD • C95 Mini Drama CD • Drama CD 2 • C97 Mini Drama CD • C98 Drama CD • Drama CD EX • Tankōbon Volume 8 Drama CD • Tankōbon Volume 9 Drama CD
Other Series		Niwasaki Diary • Idol Stuff
Songs		From Here

Anime
Episodes		1. Mahiro's Confusing New Body • 2. Mahiro's Time of the Month • 3. Mahiro's Close Encounter • 4. Mahiro's New Friend • 5. Mahiro Discovers Adventure and Social Gatherings • 6. Mahiro Goes Back to Middle School • 7. Mahiro's Role-Playing Game • 8. Mahiro's First Girls Sleepover • 9. Mahiro Rings in the New Year • 10. Mahiro Ponders Boobs and Identity • 11. Mahiro Pretties Up • 12. Mahiro's Future as a Sister
Music		Identeitei Meltdown • Himegoto*Crisisters

Locations
Cities/Towns		Onimai • Dōzan Onsen
Houses		Oyama Residence • Hozuki Residence • Ōka Residence • Murosaki Residence • Azuma/Tenkawa Residence • Senkawa Residence
Stores		Lingerie Shop • Neon • Like • Owsan Shop • Hair Salon • Apparel Shop • Tachikawa Bookstore • Hasegawa Stationary • Laundry
Restaurants		Fruit Parlor • Crepe • Wucd • Star Cafe
Schools		Yotsuba University Affiliated Junior High School
Entertainment		Mountain Hot Spring • Cinemas • Arcade • Tsukimi Inn • Karaoke Kingdom • Oshimaen • Municipal Library

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