★ 9.11
Rating
♥ 51.8K
Follows
Onii-chan wa Oshimai!
Synopsis
Read Onii-chan wa Oshimai! in English with 200 chapters on KOMIKCAST. This Manga (JP) created by Nekotoufu has a rating of 9.11 and is followed by 51.8K people.
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)
 Official Melon Books
 Official Toranoana
 Official DLSite (jp)
... Enjoy the latest updates of Onii-chan wa Oshimai! for free only at KOMIKCAST.
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)
 Official Melon Books
 Official Toranoana
 Official DLSite (jp)
... Enjoy the latest updates of Onii-chan wa Oshimai! for free only at KOMIKCAST.
Chapters List
200 Total
106
Mahiro and Sharing Secrets
Nov 29, 2025
14p
daily multivitamin
105
Mahiro and an Offline Adventure
Oct 25, 2025
15p
daily multivitamin
104
Mahiro and Mother's Day
Sep 27, 2025
14p
daily multivitamin
103
Mahiro and Heaven or Hell
Aug 30, 2025
14p
daily multivitamin
102.2
Aoi-chan Edition
Nov 01, 2025
6p
Unknown
102.1
Niichi-chan Edition
Nov 01, 2025
3p
Unknown
102
Mahiro and a Technological Nightmare
Jul 26, 2025
14p
daily multivitamin
101
Mahiro and a Celebration
Jun 28, 2025
14p
daily multivitamin
100.9
Onii-chan's Drawing Book
Nov 01, 2025
5p
Unknown
100
Mahiro and a Good Day for an Experiment
May 31, 2025
13p
daily multivitamin
99.5
Mahiro and Getting a License + Doujin Issue 33 Extras
Jul 08, 2025
7p
daily multivitamin
99
Mahiro and the Autobahn
Apr 26, 2025
13p
daily multivitamin
98.5
Mahiro and Being a Small Fry Human
Jul 08, 2025
2p
daily multivitamin
98
Mahiro and a One-Night Stay
Mar 29, 2025
15p
daily multivitamin
97
Mahiro and Crossing the Line
Feb 22, 2025
13p
daily multivitamin
96
Mahiro and a Token of Appreciation
Jan 25, 2025
14p
daily multivitamin
95.9
Minato-kun is Done For? 2
Jan 01, 2025
29p
daily multivitamin
95.5
Miyo and the Date
Mar 01, 2025
8p
daily multivitamin
95
Mahiro and the University Expedition Squad
Dec 28, 2024
14p
daily multivitamin
94
Mahiro and the New School Year, Once Again
Nov 30, 2024
16p
daily multivitamin
93.5
The Boys and Another Shot
Jan 11, 2025
4p
daily multivitamin
93
Mahiro and a Special Treat
Oct 26, 2024
13p
daily multivitamin
92.5
Asahi and Growth
Jan 11, 2025
1p
daily multivitamin
92
Mahiro and a Maiden's Secret
Sep 28, 2024
13p
daily multivitamin
91.5
Nemu and Nodoka
Jan 11, 2025
2p
daily multivitamin
91
Mahiro and Marriage
Aug 31, 2024
15p
daily multivitamin
90.9
Volume 9 Special Edition Extras
Oct 19, 2024
3p
daily multivitamin
90.8
Mahiro and Mama (Revisited)
Oct 19, 2024
9p
daily multivitamin
90.5
Chapter 90.5
Aug 17, 2024
6p
daily multivitamin
90
Mahiro and Celebrating Success
Jul 27, 2024
15p
daily multivitamin
89
Mahiro and a Home Visit
Jun 29, 2024
16p
daily multivitamin
88.5
Chapter 88.5
Aug 17, 2024
1p
daily multivitamin
88
Mahiro and Romantic Antics
May 25, 2024
15p
daily multivitamin
87
Mahiro and Special Techniques
Apr 27, 2024
15p
daily multivitamin
86.9
Minato-kun is Done For? 1.5
Apr 10, 2024
7p
daily multivitamin
86.5
Special: Asahi's Birthday
Sep 20, 2024
6p
京都府京都市右京区嵯峨二尊院門前善光寺山町２２
86
Mahiro and Overflowing Maternal Instincts
Mar 30, 2024
14p
daily multivitamin
85.5
Chapter 85.5
Jun 01, 2024
8p
daily multivitamin
85
Mahiro and a Stressful Reunion (Part 2)
Feb 24, 2024
15p
daily multivitamin
84
Mahiro and a Stressful Reunion (Part 1)
Jan 27, 2024
15p
daily multivitamin
83.9
Minato-kun is Done For? (Full Version)
Jan 07, 2024
32p
daily multivitamin
83
Mahiro and the New Year's Tour
Dec 31, 2023
15p
daily multivitamin
82.5
Chapter 82.5
Mar 02, 2024
8p
daily multivitamin
82
Mahiro and a Silent Night
Nov 25, 2023
15p
daily multivitamin
81.9
Minato-kun is Done For? (Preview Version)
Nov 11, 2023
8p
daily multivitamin
81.8
Non-Mahiro Special: Aoi-chan Edition
Nov 04, 2025
5p
MangaDex Scans
81.5
Chapter 81.5
Jan 02, 2024
6p
daily multivitamin
81
Mahiro and Conflicting Views
Oct 28, 2023
15p
daily multivitamin
80.8
Mahiro and the Growing Gal Gang + Volume 8 Extras
Dec 09, 2023
15p
daily multivitamin
80
Mahiro and the Secret Engagement
Sep 30, 2023
15p
daily multivitamin
79
Mahiro and the Gal Gang
Aug 26, 2023
15p
daily multivitamin
78.9
Mihari's Research Lab
Aug 16, 2023
26p
Unknown
78.5
The Boys and MMORPGs
Aug 14, 2023
4p
daily multivitamin
78
Mahiro and MMORPGs Revisited
Jul 29, 2023
15p
daily multivitamin
77
Mahiro and the Farewell Party
Jun 24, 2023
16p
daily multivitamin
76.9
The Research Lab's Mihari-chan
Jun 04, 2023
7p
Unknown
76.1
Blu-Ray Box Volume 2 Add-in Comic
Jun 22, 2023
6p
Unknown
76
Mahiro and a Close Call
May 27, 2023
17p
daily multivitamin
75
Mahiro and the Siren's Call
Apr 29, 2023
16p
daily multivitamin
74.99
Mihari's Birthday Venue
Apr 22, 2023
1p
Unknown
74.5
Everyone and the Blackout
May 06, 2023
6p
daily multivitamin
74.1
Blu-Ray Box Volume 1 Add-in Comic
Apr 21, 2023
6p
Unknown
74
Mahiro and a Night Together
Jul 05, 2025
13p
daily multivitamin
73.5
Non-Mahiro Special: Nii-chan Edition
Nov 07, 2025
2p
MangaDex Scans
73.1
Mahiro-chan's Birthday Venue (2023)
Apr 12, 2023
1p
IchiuzYluu
73
Mahiro and Big Bro's Secrets
Mar 20, 2023
14p
/a/nonymous
72.9
The Boys Are Done For Too! + Omnibus 22-23-24 Extras
Aug 15, 2024
18p
daily multivitamin
72
Mahiro and an Admiration
Feb 20, 2023
14p
Unknown
71.5
Mahiro and the Magazine Model
Mar 29, 2023
7p
daily multivitamin
71
Mahiro and the selfie boom
Jan 18, 2023
14p
Unknown
70.9
Volume 7 Special Booklet
Apr 07, 2023
24p
daily multivitamin
70.8
Volume 7 Extras
Mar 23, 2023
14p
daily multivitamin
70.7
Mahiro and a Discussion on Cosplay
Mar 23, 2023
7p
daily multivitamin
70
Mahiro and an autumn outing
Dec 13, 2022
14p
Unknown
69.99
Nayutan's Birthday Venue
Apr 11, 2023
2p
Unknown
69.5
Mahiro and a Moment of Glory
Mar 23, 2023
7p
daily multivitamin
69
Mahiro and the Youthful Sports Festival
Nov 14, 2022
17p
Unknown
68.99
Momiji Birthday Venue
Apr 11, 2023
2p
Unknown
68
Mahiro and the World of Hobbies
Oct 19, 2022
14p
Unknown
67.99
Kaede-chan's birthday venue
Apr 11, 2023
2p
Unknown
67
Mahiro and Male Pride
Sep 11, 2022
17p
Unknown
66.5
The Boys and Changing Shifts
Mar 22, 2023
6p
daily multivitamin
66
Mahiro and the Tempting Culture Festival (Part 2)
Aug 03, 2022
15p
Unknown
65
Mahiro and the Tempting Culture Festival (Part 1)
Jun 29, 2022
19p
Unknown
64
Mahiro and a Healthy Diet
Jun 28, 2022
20p
Unknown
63.99
Omnibus 19-20-21 Extras
Aug 29, 2023
19p
daily multivitamin
63.5
Momiji and Panties
Mar 22, 2023
6p
daily multivitamin
63
Mahiro and Staying Over Because of Rain
Apr 30, 2022
23p
Unknown
62.5
Nemu and Summer Vacation
Mar 22, 2023
4p
daily multivitamin
62.1
Mihari-chan's Birthday Venue
Apr 12, 2023
1p
IchiuzYluu
62
Mahiro and a 2nd Semester Debut
Mar 28, 2022
15p
Unknown
61
Mahiro and Summer Festival
Feb 28, 2022
18p
Unknown
60
Mahiro and Summer Homework
Feb 12, 2022
15p
Unknown
59
Mahiro and spring cleaning
Jan 28, 2022
15p
Unknown
58
Mahiro and the Marine Ranger (Part 2)
Nov 28, 2021
20p
Unknown
57
Mahiro and the Marine Ranger (Part 1)
Nov 01, 2021
33p
Unknown
56
Mahiro and The Battle Plan Meeting
Oct 13, 2021
14p
Unknown
55
Mahiro and a Summer Adventure
Aug 31, 2021
13p
Unknown
54.9
Omnibus 16-17-18 Extras
May 27, 2023
18p
Unknown
54.7
Mahiro and Harems
May 17, 2023
6p
Unknown
54.5
Mahiro and the serene mind
Dec 17, 2023
4p
ATRScans
54
Mahiro and School Ghost Stories
Jul 27, 2021
14p
Unknown
53.5
Boys and Girls
Aug 17, 2021
3p
Unknown
53
Mahiro and the North Wind and Sun
Jul 08, 2021
14p
Unknown
52
Mahiro and the Little Garden
Jul 08, 2021
13p
Unknown
51
Mahiro and Passing the Rainy Season
Jul 08, 2021
13p
Unknown
50.5
Chapter 50.5
Jul 08, 2021
4p
Unknown
50
Mahiro and Swim Classes (Part 2)
Jul 08, 2021
16p
Unknown
49
Mahiro and Swim Classes (Part 1)
Feb 25, 2021
15p
Unknown
48.5
MAHIRO AND THE PARENT-TEACHER CONFERENCE
Dec 19, 2023
5p
Unknown
48
Mahiro and Class Observation
Feb 18, 2021
13p
Unknown
47
Mahiro and the Sunny Girl
Dec 27, 2020
16p
Unknown
46.5
Mihari and Memories of Stickers
Aug 05, 2021
3p
Unknown
46
Mahiro and Sticker Collecting (fixed)
Nov 29, 2020
15p
Unknown
45.9
Omnibus 13-14-15 Extras
May 26, 2023
18p
Unknown
45.7
Mahiro and Visible Undergarments
May 20, 2023
5p
Unknown
45
Mahiro and the Season for New Clothes
Nov 09, 2020
13p
Unknown
44
Mahiro and the Secret BBQ
Oct 05, 2020
15p
Unknown
43.5
Chapter 43.5
Aug 05, 2021
6p
Unknown
43
Mahiro and Fragrances
Sep 01, 2020
14p
Unknown
42.6
EX3 Special - Mahiro and a Hair's Breadth from Danger!
Aug 31, 2020
21p
Unknown
42.5
[TEMP 1]41.3+41.7 & 42.5 & Mini Extra (2 of 10)
Aug 31, 2020
17p
Unknown
42
Mahiro and the Gift of Memories
Jul 26, 2020
16p
Unknown
41
Mahiro and the Physical Examination
Jun 28, 2020
14p
Unknown
40.99
Bonus Illustration
Aug 31, 2020
10p
Unknown
40.8
Mihari and Skipping Grades
Aug 30, 2020
13p
Unknown
40.6
Mini Extras [Complete]
Aug 30, 2020
11p
Unknown
40.5
Mahiro and Barefoot
Aug 30, 2020
2p
Unknown
40
Mahiro and an Important Secret (Part 2)
May 25, 2020
13p
Unknown
39
Mahiro and an Important Secret
Apr 26, 2020
20p
Unknown
38.5
Momiji and Massages
Aug 30, 2020
2p
Unknown
38
Mahiro and an Appreciated Break
Apr 09, 2020
19p
Unknown
37.5
Mihari and High School Girls
Aug 30, 2020
3p
Unknown
37
Mahiro and a Girl's Mannerisms
Feb 29, 2020
18p
Unknown
36.9
Mahiro's Weekday Routine + Omnibus 10-11-12 Extras
May 26, 2023
12p
Unknown
36.5
Mahiro and a Present
Aug 30, 2020
1p
Unknown
36
Mahiro and a Surprise
Jan 30, 2020
13p
Unknown
35.6
EX2 Special - I am Mahiro and I am Mihari
Jan 19, 2020
22p
Unknown
35
Mahiro and the Guidance of Fortunes
Dec 29, 2019
16p
Unknown
34.5
Chapter 34.5 (1+2+3)
Aug 30, 2020
5p
Unknown
34
Mahiro and the Adult's Door
Dec 01, 2019
14p
Unknown
33.5
Mahiro and Handmade
Aug 30, 2020
3p
Unknown
33
Mahiro and Valentine's
Oct 29, 2019
15p
Unknown
32.5
Mahiro and Drinks
Aug 30, 2020
2p
Unknown
32
Mahiro and a Surprise Visit
Sep 29, 2019
14p
Unknown
31
Mahiro and Charming Bare Legs
Sep 28, 2019
16p
Unknown
30.9
Chapter 21-30 Mini Extras [Complete]
Dec 03, 2019
21p
Unknown
30.8
Asahi and Momiji
Dec 03, 2019
9p
Unknown
30.5
Mahiro and Hot Kiss
Aug 08, 2019
7p
Unknown
30
Mahiro and the Coming and Going Year
Aug 01, 2019
19p
Unknown
29
Mahiro and a Double Date
Jun 30, 2019
14p
Unknown
28.1
Mahiro and Girl's Night (Second Part) [Tank Version]
Dec 03, 2019
20p
Unknown
28
Mahiro and Girl's Night (Second Part) [Pixiv Version]
May 29, 2019
18p
Unknown
27.99
Omnibus 7-8-9 Extras
May 26, 2023
14p
daily multivitamin
27.5
Including Extra (25.5 - 26.5 - 27.5)
May 27, 2019
10p
Unknown
27
Mahiro and Girl's Night (First Part)
Apr 28, 2019
15p
Unknown
26
Mahiro and Patissier
Apr 01, 2019
14p
Unknown
25
Mahiro and Finals
Feb 27, 2019
15p
Unknown
24.5
Part 1: Mahiro and Bento & Part 2: Mihari and Bento
May 26, 2019
8p
Unknown
24
Mahiro and Common Interests
Feb 01, 2019
17p
Unknown
23
Mahiro and the Fun Weekend
Dec 30, 2018
9p
Unknown
22.5
EX Special - Mahiro and an Uneventful Holiday
May 26, 2019
21p
Unknown
22
Mahiro and the Harsh Lesson
Nov 26, 2018
14p
Unknown
21.5
Extras
May 26, 2019
6p
Unknown
21
Mahiro and the First Day of School (V2)
Oct 31, 2018
15p
Unknown
20.9
Chapter 11-20 Mini Extras
May 25, 2019
17p
Unknown
20.5
Mihari and Dresses + Mihari (afterwards) and Dresses
May 25, 2019
9p
Unknown
20
Mahiro and Middle Schoolers (v2)
Oct 04, 2018
17p
Unknown
19
Mahiro and Uploading Videos
Aug 31, 2018
10p
Unknown
18.99
Omnibus 4-5-6 Extras
May 21, 2023
12p
daily multivitamin
18.5
Part 1: Mahiro and a "Comrade's" Return & Part 2: Mahiro and Perms
May 25, 2019
5p
Unknown
18
Mahiro and the Onsen Panic (Second Part)
Jul 30, 2018
15p
Unknown
17
Mahiro and the Onsen Panic (First Part)
Jul 07, 2018
15p
Unknown
16
Mahiro and the Hair Salon
May 27, 2018
11p
Unknown
15.5
Siblings and Kotatsu
May 25, 2019
5p
Unknown
15
Mahiro and Party Night
Apr 30, 2018
16p
Unknown
14
Mahiro and a Little Adventure
Apr 03, 2018
14p
Unknown
13
Mahiro and a Wholesome Relationship
Mar 01, 2018
15p
Unknown
12.5
Mahiro and Nichiasa
May 25, 2019
3p
Unknown
12
Mahiro and a Lonely Night
Feb 05, 2018
11p
Unknown
11
Mahiro and Adventure
Feb 05, 2018
15p
Unknown
10.99
Omnibus 1-2-3 Extras
May 17, 2023
10p
daily multivitamin
10.9
Chapter 1-10 Mini Extras
May 24, 2019
19p
Unknown
10.5
Mahiro and Helping Out & OMAKE - Mihari and Onii-chan
Jul 21, 2018
11p
Unknown
10
Mahiro and Special Home Security
Feb 03, 2018
16p
Unknown
9.5
Mahiro and the Two's Secret
Jul 21, 2018
5p
Unknown
9
Mahiro and a Girl's Vacation
Feb 03, 2018
14p
Unknown
8.5
Mahiro and Gacha (v2)
Feb 07, 2018
11p
Unknown
8
Mahiro and New Game
Feb 02, 2018
17p
Unknown
7
Mahiro and Encounters with the Unknown
Feb 02, 2018
15p
Unknown
6.5
Mahiro and Going in Circles
Jul 21, 2018
4p
Unknown
6
Mahiro and the Secret Garden
Feb 01, 2018
14p
Unknown
5.5
Mahiro and Comfort for Many Days
Jul 21, 2018
4p
Unknown
5
Mahiro and a Melancholic Day
Feb 01, 2018
13p
Unknown
4
Mahiro and MMORPG
Jan 31, 2018
14p
Unknown
3
Mahiro and Identity
Jan 31, 2018
13p
Unknown
2
Mahiro and the Dangerous Mirror
Jan 29, 2018
13p
Unknown
1.5
Mahiro and the Toilet
Jul 21, 2018
6p
Unknown
1
Mahiro and the Unpleasurable Body
Sep 28, 2024
13p
Unknown
1
Mahiro and the Unpleasurable Body
Jan 29, 2018
14p
Unknown
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