User:lol1VNIO/Manuscripts/Onimai: I'm Now Your Sister!

Last edited 03/23/2023

Ep 1
Mahiro Oyama is a ''[[hikikomori]]'' living with his grade-skipping wunderkind little sister Mihari who is a researcher. One day he wakes up as a young girl after being drugged by Mihari, as a part of her Big Brother Rehabilitation project. She forces him to take a shower and wear feminine clothes upon a health checkup. Seeing him obsess over his newfound interest in a ''[[yaoi]]'' visual novel, she takes him out for a jog and buys him a new bra; he refused to have one on for the jog in an attempt to hang onto his ever-decreasing masculinity.

Ep 2
The water heater is broken for the night, so Mihari and Mahiro visit a public bath, where the former teaches him about hair care; quickly exhausted, he leaves to reminisce about the time when he was the one helping his little sibling bathe. Upon finishing breakfast, Mahiro naturally tries out new hairstyles, which Mihari records for her research. As nearly one month passes since start of the transition, Mahiro has his first menstruation and Mihari takes care of him.

Ep 3
Mahiro meets Kaede Hozuki, a ''[[gyaru]]'' and friend of Mihari, who cooks him lunch and puts make-up on him. In a shopping mall, the three buy new clothes before watching a film—in the middle of which, Mahiro runs to the bathroom but urinates himself before he reaches it. Kaede helps him clean up and buys him new panties. Mihari catches a cold from the movie theater, so Mahiro does the housework, incompetently.

Ep 4
Mihari catches Mahiro mimicking a female television character before departing for campus, leaving him to laze around until morning. Mahiro loses in a video game match against Mihari and thus shops for grocery, where he befriends Momiji, Kaede's [[tomboy]]ish middle school sister. Days after, Mahiro swiftly tidies up his room when he sees the two sisters come over; however, he accidentally knocks over his [[hentai]] manga collection in front of Momiji.

Ep 5
Mahiro voluntarily goes outside to buy himself anime-imprint folders and gets caught by a truant officer at an arcade; he escapes the traumatic encounter and a worried Mihari thinks of initiating her plan B. Mihari takes him to a hair salon for a new style, where he is overloaded by small talks. The Oyamas and Hozukis plan a trip to an onsen while having a dinner at the latter's residence.

Ep 6
Mahiro gets to know Momiji's friends Asahi and Miyo, and learns that he has been enrolled in middle school, going in the same class with them who help him with his social anxiety in the first days. Still not fully integrated into his new body, he makes mistakes such as using the boys' restroom and changing clothes in the classroom. Because Mihari fabricated a cover story involving past medical experiences, he does not need to run a race in physical education.

Ep 7
Despite studying at least a week prior, Mahiro faces difficulties in the final examinations; in addition, he sleeps through the mathematics phase, one of the only subjects he is good at. He talks with two male classmates who share the same interests in a video game series, but quickly becomes depressed realizing that the installment he plays had been released before they were born. In home economics, Mahiro and his friends bake black tea cookies, the recipe of which is taught to him and Momiji by Kaede.

Ep 8
During winter break, Mihari secretly invites Mahiro's friends to a sleepover. They play a video game together and take a bath in two turns—both Mahiro with Mihari, and Momiji with her friends reminisce about their pasts. A game of rock-paper-scissors escalates into a pillow fight which is settled by Mihari. Asahi tells everyone a horror story before falling asleep with Mahiro's comforter; as he slides over to Momiji, she mistakes him for a monster and urinates her futon. Mahiro washes it and takes the blame for it the next morning.

Ep 9
Mihari and Kaede catch their younger siblings stalking them at a Christmas market and decide to spend quality time together. Mihari forces him to visit a shrine to ring in the New Year and offer prayers with them, joined by Asahi and Miyo. Kaede takes them all back home for dinner and lets Mihari try ''[[amazake]]'' for the first time; she becomes heavily intoxicated and gains strong romantic affection.

Ep 10
On the first day of school after the break, Mahiro and his colleagues discuss fashion during the cold months. Kaede takes tutoring lessons from Mihari and, as a reward, massages her and Mahiro. On Valentine's day, he trades chocolate bars for miscellaneous sweets with his classmates, buying an additional one for his sister in the evening. He catches the two male classmates attempting to sneak into the hentai section of a bookstore before meeting the ''[[yuri (genre)|yuri]]''-affectionate Miyo. The girls share a meal of crêpes together.

Ep 11
The class talks about a trendy book about astrology, a topic which Mihari despises. In an attempt by a ''[[chūnibyō]]'' Momiji—who believes in astrology—to get Mahiro's birth date, he realizes it is on the current day. His friends surprise him with a party the next day and give him presents, one of which is a lipstick from Kaede. He wears it to school, which gets the class' attention as it is against the rules. At home, Kaede dresses up the Oyama siblings with gyaru-style clothing.

Ep 12
As planned, they stay at an onsen together with Asahi and Miyo for one night. In the middle of playing with his friends at the pool, Mahiro's drug slowly wears off and his penis grows back. Without anyone noticing it, he storms back to the hotel room with Mihari who presents him with a backup potion but warns that its duration lasts significantly longer. After taking the evening's time to reflect on it, he decides to drink it. On the way home by train, Mihari reveals to him that her conspiring rehabilitation project has been overly successful.