Onii-chan wa Oshimai! Wiki
Advertisement
Onii-chan wa Oshimai! Wiki

See also: Onimai: I'm Now Your Sister! (anime) and Onimai

Onimai: I'm Now Your Sister! (お兄ちゃんはおしまい!, Onii-chan wa Oshimai!) is a Japanese manga series written and illustrated by Nekotofu. The series has been serialized online since 2017; it is also currently serialized in Ichijinsha's Monthly Comic Rex magazine since April 2019. It is licensed in English by Kodansha USA. An anime television series adaptation by Studio Bind ran from January 5, 2023 to March 23, 2023.

Plot[]

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[]

See also: Characters

Chapters[]

See also: List of Onimai: I'm Now Your Sister! Chapters

Written and illustrated by Nekotofu, Onimai: I'm Now Your Sister! began serialization online via Pixiv and other platforms in 2017. It also started in Ichijinsha's Monthly Comic Rex magazine on April 27, 2019. As of January 2023, seven tankōbon volumes have been released by Ichijinsha. In North America, Kodansha USA is publishing the series in English. In Germany, Manga JAM Session publishes the manga as Ab sofort Schwester!.

No. Title Publication Date
1 Mahiro's Confusing New Body February 25, 2017
1.25/Special Blu-ray Volume 1 Appendix Manga April 19, 2023
1.5 Mahiro and the Bathroom May 6, 2017
2 Mahiro Faces the Mirror March 24, 2017
3 Mahiro's Self Image April 22, 2017
4 Mahiro Plays an MMO May 27, 2017
5 Mahiro's Melancholy Day June 24, 2017
5.5 Mahiro, Even On Heavy Days August 13, 2017
6 Mahiro and the Secret Garden July 29, 2017
6.5 Mihari's Wasted Efforts August 13, 2017
7 Mahiro's Unexpected Encounter August 25, 2017
8 Mahiro Starts Over September 30, 2017
8.5 Mahiro and the Gatcha Game February 11, 2018
9 Mahiro and the Girls' Day Out October 28, 2017
9.5 Mahiro and Kaede's Secret December 31, 2017
10 Mahiro the Own-Home Security Guard November 27, 2017
10.5 Mahiro Helps Out June 27, 2018 (Japan)

August 31, 2021 (North America)

Bonus Mihari and Her Onii-Chan June 27, 2018 (Japan)

August 31, 2021 (North America)

Special Mahiro and the Uneventful Holiday December 31, 2018
11 Mahiro Falls in Love December 27, 2017
12 Mahiro's Night Alone January 27, 2018
12.5 Mahiro's Sunday Morning February 11, 2018
13 Mahiro's Wholesome Playdate February 24, 2018
14 Mahiro's Little Adventure March 31, 2018
15 Mahiro Attends a Party April 28, 2018
15.5 Siblings Share the Kotatsu April 30, 2018
Special Real Record! Drama CD Report April 30, 2018
16 Mahiro Visits the Salon May 26, 2018
17 Mahiro's Panic! At the Hot Spring (Part 1) June 30, 2018
18 Mahiro's Panic! At the Hot Spring (Part 2) July 28, 2018
18.5 (Part 1) Mahiro and the Comrade's Return August 12, 2018
18.5 (Part 2) Mahiro's Perm August 12, 2018
18.75/Special Blu-ray Volume 2 Appendix Manga June 21, 2023
Special Mahiro and the After-Travel Party August 11, 2019
19 Mahiro the Streamer August 29, 2018
20 Mahiro and the Middle Schoolers September 29, 2018
Bonus Mihari's Wardrobe January 26, 2019 (Japan)

October 5, 2021 (North America)

Bonus Mihari's Wardrobe Afterwards January 26, 2019 (Japan)

October 5, 2021 (North America)

21 Mahiro's First Day October 28, 2018.
Bonus Miyo's Refusal November 25, 2018
Bonus Momiji's Nickname November 25, 2018
Bonus Kaede's Concern November 25, 2018
22 Mahiro's Difficult Class November 24, 2018
23 Mahiro's Exciting Weekend December 29, 2018
Bonus Later in the Lab December 31, 2018
24 Mahiro and Conversation January 26, 2019
Bonus Mahiro's Lunch February 17, 2019
Bonus Mihari's Lunch February 17, 2019
25 Mahiro's Final Exams February 23, 2019
25.5 Mahiro's Touch April 29, 2019
Bonus Asahi's Innocence November 25, 2018
26 Mahiro the Patissier March 30, 2019
26.5 Mahiro's Twisted Logic April 29, 2019
27 Mahiro's Sleepover (Part 1) April 27, 2019
27.5 Mahiro's Sibling Bathtime April 29, 2019
28 Mahiro's Sleepover (Part 2) May 27, 2019
29 Mahiro's Double Date June 29, 2019
30 Mahiro Rings in the New Year July 27, 2019
30.5 Mahiro and the Spicy Kiss August 6, 2019
Bonus Asahi and Momiji September 27, 2019 (Japan)

November 30, 2021 (North America)

31 Mahiro and the Allure of Bare Legs August 31, 2019
32 Mahiro and the Unexpected Guests September 28, 2019
32.5 Mahiro and the Mystery Brew December 30, 2019
33 Mahiro on Valentine's Day October 29, 2019
33.5 Mahiro and the Homemade Chocolate December 30, 2019
34 Mahiro and the Adults Only Section November 30, 2019
34.5 (Part 1) Asahi's Crepe February 9, 2020
34.5 (Part 2) Mahiro's Yuri Manga February 9, 2020
34.5 (Part 3) Mahiro's "Something" February 9, 2020
35 Mahiro and the Guidance of the Stars December 28, 2019
Special Mahiro is Me and Mihari is Me December 30, 2019
36 Mahiro's Surprise Party January 25, 2020
36.5 Mahiro's Final Present February 9, 2020
37 Mahiro Pretties Up February 24, 2020
37.5 Mihari and the High School Girls May 2, 2020
38 Mahiro's Relaxing Day Off March 28, 2020
38.5 Momiji's Massage May 2, 2020
39 Mahiro's Big Secret (Part 1) April 25, 2020
40 Mahiro's Big Secret (Part 2) May 24, 2020
40.5 Mahiro's Bare Feet August 15, 2020
Bonus Mihari's Skipped Grades July 27, 2020 (Japan)

January 25, 2022 (North America)

41 Mahiro and the School Physical June 24, 2020
41.3 Mahiro and the Health Committee August 15, 2020
41.7 Mahiro and the Spankies August 15, 2020
42 Mahiro and the Gifted Experience July 25, 2020
42.5 Mihari and the Stuffed Animal August 15, 2020
Special Mahiro in a Close Call August 15, 2020
Special 2020 Summer Special Brochure August 15, 2020
43 Mahiro and the Perfume August 29, 2020
43.5 Mahiro and the Full-Cup Bra December 30, 2020
44 Mahiro and the Barbecue Secret September 26, 2020
45 Mahiro and the Seasonal Attire October 24, 2020
46 Mahiro and the Sticker Collection November 28, 2020
46.5 Mihari's Sticker Memories February 21, 2021
47 Mahiro and the Sunshine Girl December 26, 2020
Special Mahiro and a Sleepy Day December 30, 2020
47.5 Kaede's Nickname February 21, 2021
48 Mahiro and Visitation Day January 30, 2021
48.5 Mahiro and the Parent-Teacher Conference February 21, 2021
49 Mahiro and Swim Class (Part 1) February 23, 2021
50 Mahiro and Swim Class (Part 2) March 27, 2021
50.5 Mahiro and the Comrade's Return Again May 2, 2021
Bonus Nayuta's Recent Past May 27, 2021 (Japan)

March 22, 2022 (North America)

Special Mahiro's Colorful Life April 27, 2022
51 Mahiro and the Rainy Season April 24, 2021
51.5 Mahiro and Self-Styling May 2, 2021
52 Mahiro and the Little Garden May 27, 2021
53 Mahiro, the Sun, and the Northern Wind June 26, 2021
53.5 Girls and Boys August 14, 2021
54 Mahiro and the After-School Fright July 24, 2021
54.5 Mahiro's Cool Head August 14, 2021
55 Mahiro and the Midsummer Romance August 27, 2021
56 Mahiro and the Strategy Meeting September 25, 2021
56.5 (Part 1) Nayuta's Swimsuit December 31, 2021
56.5 (Part 2) Kaede and the Junior High Girls December 31, 2021
57 Mahiro's Beach Fun (Part 1) October 30, 2021
58 Mahiro's Beach Fun (Part 2) November 27, 2021
58.5 Mahiro and the Squishy Thingie February 20, 2022
59 Mahiro's Deep Clean December 25, 2021
Special Mahiro's Weekday Routine December 31, 2021
60 Mahiro's Summer Homework January 22, 2022
Special Doujinshi Volume 20 Commemorative Manga February 22, 2022
Bonus Mahiro and the Photo Albums April 22, 2022 (Japan)

October 25, 2022 (North America)

Special Mahiro's Anime Time January 7, 2023 (Japan)

July 25, 2023 (North America)

61 Mahiro and the Summer Festival February 26, 2022
Special Mahiro and After the Festival August 13, 2023
62 Mahiro's Second Semester Debut March 26, 2022
62.5 Nemu's Summer Vacation May 5, 2022
63 Mahiro Shelters From the Storm April 30, 2022
63.5 Momiji's Panty Problem May 5, 2022
64 Mahiro's Weight-Loss Plan May 28, 2022
65 Mahiro and the Charming School Festival (Part 1) June 25, 2022
66 Mahiro and the Charming School Festival (Part 2) July 30, 2022
66.5 The Boys' Shift Change August 13, 2022
67 Mahiro's Masculine Ego August 27, 2022
Special Mahiro and the Visible Undergarmets August 31, 2022
68 Mahiro and the Fan World September 24, 2022
69 Mahiro's Field Day October 29, 2022
69.5 Mahiro's Cheer Wear December 31, 2022
70 Mahiro's Autumn Outing November 26, 2022
Bonus Mahiro's Cosplay Round-Table January 7, 2023 (Japan)

July 25, 2023 (North America)

Special Miyo and the Enchanted Night January 31, 2023
Special Asahi and Nii-chan January 31, 2023
Special Perfect Onee-chan January 31, 2023
Special Mihari's Research Lab January 31, 2023
71 Mahiro and the Selfie Craze December 26, 2022
Special Mahiro and the Harem December 31, 2022
71.5 Mahiro and the Amateur Model February 19, 2023
72 Mahiro and Admiration January 27, 2023
73 Mahiro and the Brother's Secrets February 25, 2023
74 Mahiro and Their Night Together March 25, 2023
74.5 Everyone and the Power Outage May 5, 2023
75 Mahiro and the Devilish Girl April 29, 2023
76 Mahiro and the Crisis May 27, 2023
Special A Story Where That Grows May 27, 2023
77 Mahiro and the Going-Away Party June 24, 2023
78 Mahiro Plays an MMO, Again July 29, 2023
78.5 The Boys Play an MMO August 13, 2023
Special Mihari and the Drinking Party August 13, 2023
Special A Story Where That Grows Part 2 August 13, 2023
79 Mahiro and the Gal Squad August 26, 2023
80 Mahiro and the Secret Rendezvous September 30, 2023
Bonus Mahiro and the Ko-Gal Squad November 27, 2023 (Japan)

June 18, 2024 (North America)

Chapters Not Yet Released in North America[]

No. Title Publication Date
Special TBA September 27, 2024
81 TBA October 28, 2023
81.5 TBA January 1, 2024
82 TBA November 25, 2023
82.5 TBA February 24, 2024
83 TBA January 1, 2024
Special Minato-kun is Done For? January 1, 2024
Bonus Offline Meeting Night January 1, 2024
84 TBA Janury 27, 2024
85 TBA February 24, 2024
85.5 TBA May 26, 2024
86 TBA March 30, 2024
Special Minato-kun is Done For? 1.5 April 7, 2024
87 TBA April 26, 2024
88 TBA May 26, 2024
88.5 TBA August 12, 2024
89 TBA June 28, 2024
90 TBA July 26, 2024
90.5 TBA August 12, 2024
Bonus TBA September 27, 2024
Special The Boys Are Done For! August 12, 2024
91 TBA August 31, 2024
91.5 TBA December 29, 2024
92 TBA September 28, 2024
92.5 TBA December 29, 2024
93 TBA October 26, 2024
93.5 TBA December 29, 2024
94 TBA November 29, 2024
95 TBA December 28, 2024
95.5 TBA February 16, 2025
Special Minato-kun is Done For? 2 December 29, 2024
96 TBA January 24, 2025
97 TBA February 22, 2025

Volumes[]

Onii-chan wa Oshimai! Wiki • Navigation
Manga
Doujinshi 1234567891011121314151617181920212223242526272829303132
Collected Works 12345678
Tankōbon 123456789
EX Specials EX SpecialEX2 SpecialEX3 Special
Spin-off Doujinshi Good Night Onii-chan!Mihari-chan in the LaboratoryOnimai Side Reader: Mihari's Laboratory
Minato-kun is Done For? 11.52
Anthology 12345
Drama CDs Drama CDC95 Mini Drama CDDrama CD 2C97 Mini Drama CDC98 Drama CDDrama CD EXTankōbon Volume 8 Drama CDTankōbon Volume 9 Drama CD
Other Series Niwasaki DiaryIdol Stuff
Songs From Here
Advertisement