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Onii-chan wa Oshimai!
✍️ Nekotoufu 13,787 viewsOngoing
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](https://www.melonbooks.co.jp/circle/index.php?circle_id=3753)  [Official Toranoana](https://ec.toranoana.shop/tora/ec/cot/circle/2UPA116P847KdC6Rd687/all/)  [Official DLSite](https://www.dlsite.com/home/circle/profile/=/maker_id/RG40614.html) (jp)
Chapters(217 chapters)
Language:
Chapter 115- Mahiro and the Joys of Creation
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Chapter 114- Mahiro and the Cosplay Photoshoot
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Chapter 113- Mahiro and the Ecological Research Duo
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Chapter 112.5- MAHIRO AND THE SUCCUBUS DRESS
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Chapter 112- Mahiro and Gender Topsy-Turvy
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Chapter 111.5- MAHIRO AND THE SECOND ROUND
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Chapter 111- Mahiro and the Fun-filled Lion's Den
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Chapter 110- Mahiro and the Demon of the Prefect Council
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Chapter 109- Mahiro and a Healthy Beauty Regimen
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Chapter 108.5- A DATE WITH NEMU
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Chapter 108- Mahiro and Bodyguards
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Chapter 107.9- Minato-kun is Done For? 3
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Chapter 107.5- MAHIRO AND THE MAKEOVER
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Chapter 107- Mahiro and Popularity Rankings
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Chapter 106- Mahiro and Sharing Secrets
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Chapter 105- Mahiro and an Offline Adventure
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Chapter 104.5- MAHIRO AND THE MOTHERLY EMBRACE
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Chapter 104- Mahiro and Mother's Day
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Chapter 103- Mahiro and Heaven or Hell
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Chapter 102.2- Aoi-chan Edition
N/A
Chapter 102.1- Niichi-chan Edition
N/A
Chapter 102- Mahiro and a Technological Nightmare
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Chapter 101.5- MAHIRO AND THE FEMALE CHARACTERS
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Chapter 101- Mahiro and a Celebration
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Chapter 100.9- Onii-chan's Drawing Book
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Chapter 100.5- MAHIRO AND THE CAT ARMY......
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Chapter 100- Mahiro and a Good Day for an Experiment
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Chapter 99.5- Mahiro and Getting a License + Doujin Issue 33 Extras
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Chapter 99- Mahiro and the Autobahn
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Chapter 98.5- Mahiro and Being a Small Fry Human
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Chapter 98- Mahiro and a One-Night Stay
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Chapter 97- Mahiro and Crossing the Line
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Chapter 96- Mahiro and a Token of Appreciation
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Chapter 95.9- Minato-kun is Done For? 2
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Chapter 95.5- Miyo and the Date
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Chapter 95- Mahiro and the University Expedition Squad
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Chapter 94- Mahiro and the New School Year, Once Again
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Chapter 93.5- The Boys and Another Shot
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Chapter 93- Mahiro and a Special Treat
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Chapter 92.5- Asahi and Growth
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Chapter 92- Mahiro and a Maiden's Secret
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Chapter 91.5- Nemu and Nodoka
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Chapter 91- Mahiro and Marriage
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Chapter 90.9- Volume 9 Special Edition Extras
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Chapter 90.8- Mahiro and Mama (Revisited)
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Chapter 90.5
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Chapter 90- Mahiro and Celebrating Success
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Chapter 89- Mahiro and a Home Visit
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Chapter 88.5
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Chapter 88- Mahiro and Romantic Antics
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Chapter 87- Mahiro and Special Techniques
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Chapter 86.9- Minato-kun is Done For? 1.5
N/A
Chapter 86.5- Special: Asahi's Birthday
N/A
Chapter 86- Mahiro and Overflowing Maternal Instincts
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Chapter 85.5
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Chapter 85- Mahiro and a Stressful Reunion (Part 2)
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Chapter 84- Mahiro and a Stressful Reunion (Part 1)
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Chapter 83.9- Minato-kun is Done For? (Full Version)
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Chapter 83- Mahiro and the New Year's Tour
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Chapter 82.5
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Chapter 82- Mahiro and a Silent Night
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Chapter 81.9- Minato-kun is Done For? (Preview Version)
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Chapter 81.8- Non-Mahiro Special: Aoi-chan Edition
N/A
Chapter 81.5- Chapter 81.5
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Chapter 81- Mahiro and Conflicting Views
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Chapter 80.8- Mahiro and the Growing Gal Gang + Volume 8 Extras
N/A
Chapter 80- Mahiro and the Secret Engagement
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Chapter 79- Mahiro and the Gal Gang
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Chapter 78.9- Mihari's Research Lab
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Chapter 78.5- The Boys and MMORPGs
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Chapter 78- Mahiro and MMORPGs Revisited
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Chapter 77- Mahiro and the Farewell Party
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Chapter 76.9- The Research Lab's Mihari-chan
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Chapter 76.1- Blu-Ray Box Volume 2 Add-in Comic
N/A
Chapter 76- Mahiro and a Close Call
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Chapter 75- Mahiro and the Siren's Call
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Chapter 74.99- Mihari's Birthday Venue
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Chapter 74.5- Everyone and the Blackout
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Chapter 74.1- Blu-Ray Box Volume 1 Add-in Comic
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Chapter 74- Mahiro and a Night Together
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Chapter 73.5- Non-Mahiro Special: Nii-chan Edition
N/A
Chapter 73.1- Mahiro-chan's Birthday Venue (2023)
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Chapter 73- Mahiro and Big Bro's Secrets
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Chapter 72.9- The Boys Are Done For Too! + Omnibus 22-23-24 Extras
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Chapter 72- Mahiro and an Admiration
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Chapter 71.5- Mahiro and the Magazine Model
N/A
Chapter 71- Mahiro and the selfie boom
N/A
Chapter 70.9- Volume 7 Special Booklet
N/A
Chapter 70.8- Volume 7 Extras
N/A
Chapter 70.7- Mahiro and a Discussion on Cosplay
N/A
Chapter 70- Mahiro and an autumn outing
N/A
Chapter 69.99- Nayutan's Birthday Venue
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Chapter 69.5- Mahiro and a Moment of Glory
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Chapter 69- Mahiro and the Youthful Sports Festival
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Chapter 68.99- Momiji Birthday Venue
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Chapter 68- Mahiro and the World of Hobbies
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Chapter 67.99- Kaede-chan's birthday venue
N/A
Chapter 67- Mahiro and Male Pride
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Chapter 66.5- The Boys and Changing Shifts
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Chapter 66- Mahiro and the Tempting Culture Festival (Part 2)
N/A
Chapter 65- Mahiro and the Tempting Culture Festival (Part 1)
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Chapter 64- Mahiro and a Healthy Diet
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Chapter 63.99- Omnibus 19-20-21 Extras
N/A
Chapter 63.5- Momiji and Panties
N/A
Chapter 63- Mahiro and Staying Over Because of Rain
N/A
Chapter 62.5- Nemu and Summer Vacation
N/A
Chapter 62.1- Mihari-chan's Birthday Venue
N/A
Chapter 62- Mahiro and a 2nd Semester Debut
N/A
Chapter 61- Mahiro and Summer Festival
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Chapter 60- Mahiro and Summer Homework
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Chapter 59- Mahiro and spring cleaning
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Chapter 58- Mahiro and the Marine Ranger (Part 2)
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Chapter 57- Mahiro and the Marine Ranger (Part 1)
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Chapter 56- Mahiro and The Battle Plan Meeting
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Chapter 55- Mahiro and a Summer Adventure
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Chapter 54.9- Omnibus 16-17-18 Extras
N/A
Chapter 54.7- Mahiro and Harems
N/A
Chapter 54.5- Mahiro and the serene mind
N/A
Chapter 54- Mahiro and School Ghost Stories
N/A
Chapter 53.5- Boys and Girls
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Chapter 53- Mahiro and the North Wind and Sun
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Chapter 52- Mahiro and the Little Garden
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Chapter 51- Mahiro and Passing the Rainy Season
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Chapter 50.5
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Chapter 50- Mahiro and Swim Classes (Part 2)
N/A
Chapter 49- Mahiro and Swim Classes (Part 1)
N/A
Chapter 48.5- MAHIRO AND THE PARENT-TEACHER CONFERENCE
N/A
Chapter 48- Mahiro and Class Observation
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Chapter 47- Mahiro and the Sunny Girl
N/A
Chapter 46.5- Mihari and Memories of Stickers
N/A
Chapter 46- Mahiro and Sticker Collecting (fixed)
N/A
Chapter 45.9- Omnibus 13-14-15 Extras
N/A
Chapter 45.7- Mahiro and Visible Undergarments
N/A
Chapter 45- Mahiro and the Season for New Clothes
N/A
Chapter 44- Mahiro and the Secret BBQ
N/A
Chapter 43.5
N/A
Chapter 43- Mahiro and Fragrances
N/A
Chapter 42.6- EX3 Special - Mahiro and a Hair's Breadth from Danger!
N/A
Chapter 42.5- [TEMP 1]41.3+41.7 & 42.5 & Mini Extra (2 of 10)
N/A
Chapter 42- Mahiro and the Gift of Memories
N/A
Chapter 41- Mahiro and the Physical Examination
N/A
Chapter 40.99- Bonus Illustration
N/A
Chapter 40.8- Mihari and Skipping Grades
N/A
Chapter 40.6- Mini Extras [Complete]
N/A
Chapter 40.5- Mahiro and Barefoot
N/A
Chapter 40- Mahiro and an Important Secret (Part 2)
N/A
Chapter 39- Mahiro and an Important Secret
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Chapter 38.5- Momiji and Massages
N/A
Chapter 38- Mahiro and an Appreciated Break
N/A
Chapter 37.5- Mihari and High School Girls
N/A
Chapter 37- Mahiro and a Girl's Mannerisms
N/A
Chapter 36.9- Mahiro's Weekday Routine + Omnibus 10-11-12 Extras
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Chapter 36.5- Mahiro and a Present
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Chapter 36- Mahiro and a Surprise
N/A
Chapter 35.6- EX2 Special - I am Mahiro and I am Mihari
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Chapter 35- Mahiro and the Guidance of Fortunes
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Chapter 34.5- Chapter 34.5 (1+2+3)
N/A
Chapter 34- Mahiro and the Adult's Door
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Chapter 33.5- Mahiro and Handmade
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Chapter 33- Mahiro and Valentine's
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Chapter 32.5- Mahiro and Drinks
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Chapter 32- Mahiro and a Surprise Visit
N/A
Chapter 31- Mahiro and Charming Bare Legs
N/A
Chapter 30.9- Chapter 21-30 Mini Extras [Complete]
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Chapter 30.8- Asahi and Momiji
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Chapter 30.5- Mahiro and Hot Kiss
N/A
Chapter 30- Mahiro and the Coming and Going Year
N/A
Chapter 29- Mahiro and a Double Date
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Chapter 28.1- Mahiro and Girl's Night (Second Part) [Tank Version]
N/A
Chapter 28- Mahiro and Girl's Night (Second Part) [Pixiv Version]
N/A
Chapter 27.99- Omnibus 7-8-9 Extras
N/A
Chapter 27.5- Including Extra (25.5 - 26.5 - 27.5)
N/A
Chapter 27- Mahiro and Girl's Night (First Part)
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Chapter 26- Mahiro and Patissier
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Chapter 25- Mahiro and Finals
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Chapter 24.5- Part 1: Mahiro and Bento & Part 2: Mihari and Bento
N/A
Chapter 24- Mahiro and Common Interests
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Chapter 23- Mahiro and the Fun Weekend
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Chapter 22.5- EX Special - Mahiro and an Uneventful Holiday
N/A
Chapter 22- Mahiro and the Harsh Lesson
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Chapter 21.5- Extras
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Chapter 21- Mahiro and the First Day of School (V2)
N/A
Chapter 20.9- Chapter 11-20 Mini Extras
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Chapter 20.5- Mihari and Dresses + Mihari (afterwards) and Dresses
N/A
Chapter 20- Mahiro and Middle Schoolers (v2)
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Chapter 19- Mahiro and Uploading Videos
N/A
Chapter 18.99- Omnibus 4-5-6 Extras
N/A
Chapter 18.5- Part 1: Mahiro and a "Comrade's" Return & Part 2: Mahiro and Perms
N/A
Chapter 18- Mahiro and the Onsen Panic (Second Part)
N/A
Chapter 17- Mahiro and the Onsen Panic (First Part)
N/A
Chapter 16- Mahiro and the Hair Salon
N/A
Chapter 15.5- Siblings and Kotatsu
N/A
Chapter 15- Mahiro and Party Night
N/A
Chapter 14- Mahiro and a Little Adventure
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Chapter 13- Mahiro and a Wholesome Relationship
N/A
Chapter 12.5- Mahiro and Nichiasa
N/A
Chapter 12- Mahiro and a Lonely Night
N/A
Chapter 11- Mahiro and Adventure
N/A
Chapter 10.99- Omnibus 1-2-3 Extras
N/A
Chapter 10.9- Chapter 1-10 Mini Extras
N/A
Chapter 10.5- Mahiro and Helping Out & OMAKE - Mihari and Onii-chan
N/A
Chapter 10- Mahiro and Special Home Security
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Chapter 9.5- Mahiro and the Two's Secret
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Chapter 9- Mahiro and a Girl's Vacation
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Chapter 8.5- Mahiro and Gacha (v2)
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Chapter 8- Mahiro and New Game
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Chapter 7- Mahiro and Encounters with the Unknown
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Chapter 6.5- Mahiro and Going in Circles
N/A
Chapter 6- Mahiro and the Secret Garden
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Chapter 5.5- Mahiro and Comfort for Many Days
N/A
Chapter 5- Mahiro and a Melancholic Day
N/A
Chapter 4- Mahiro and MMORPG
N/A
Chapter 3- Mahiro and Identity
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Chapter 2- Mahiro and the Dangerous Mirror
N/A
Chapter 1.5- Mahiro and the Toilet
N/A
Chapter 1- Mahiro and the Unpleasurable Body
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Chapter 1- Mahiro and the Unpleasurable Body
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