Mahiro's Sleepover (Part 1)

Mahiro's Sleepover (Part 1) (まひろとガールズナイト（前編）, Mahiro To Gāruzu Naito (Zenpen)) is Chapter 27 of Onimai: I'm Now Your Sister!. It was originally published on Pixiv on April 27, 2019.

Summary
Concerned that Mahiro might backslide during winter break, Mihari arranges a sleepover at their house with Momiji, Asahi, and Miyo.

Plot
It's nighttime at the Oyama household. Mihari serves dinner and says to eat up as there is plenty to go around. It is revealed that Momiji, Asahi, and Miyo are eating dinner with Mahiro and Mihari. Mahiro is excited that they are having meatloaf. Asahi tells Mihari that she is a great cook, calling her "Dr. Oyama". Embarrassed, Mihari says that she isn't a doctor which makes Mahiro laugh. Miyo says to Mihari that she'll have to give her the recipie later. Momiji tells Miyo to pace herself there. As the group continues to eat dinner and chat, Mahiro narrates the events that led them to gathering there in the first place.

Earlier that day, Mahiro jumps for joy over it being winter break, calling it the best. She remarks that through fire and flames, they have finally reached paradise. She adds that now that school is out she can be as laid back as she wants and lies facedown on the couch to rest.

Mihari groans upon seeing this. She realizes that extended vacations might be trouble, and that if she doesn't step in Mahiro might backslide disastrously. She decides that she has to do something and starts tapping her phone.

Mahiro decides that if she wants to use her free time to the fullest, she'll need to divide up all her relaxation activities and decides to sketch out a schedule. She decides that she wants to sleep in late, and save less intense things for nighttime, ultimately coming up with a pie chart representing her planned activities:


 * 23:00 - 3:00 - Anime
 * 3:00 - 11:30 - Sleep
 * 11:30 - 12:30 - Lunch
 * 12:30 - 18:00 - Video Games
 * 18:00 - 19:00 - Dinner
 * 19:00 - 23:00 - Manga

As she finishes, Mahiro stares at her work in awe remarking how perfect it is. She decides that with that settled, it is time to start the main event: video games until dinner. Mihari asks if that is what she usually does anyway, but Mahiro doesn't answer her. Mahiro soon gets a bit bored and asks Mihari if she wants to play with her. Mihari says that she can't do it today.

Mahiro is left feeling weird, noticing that today feels so off. She even notes that she's been looking forward to this alone time for so long, but now that it's here she's not that into it.

The doorbell rings, and Mihari notes that "they're" here. Mahiro wonders if that means what she thinks it does. It turns out to be Momiji, Asahi, and Miyo. Asahi says hi while Momiji says to pardon the intrusion. Mahiro is overwhelmed at all of them showing up at once, and remarks the she won't fall for it this time, not wanting to do anymore homework like what happened the last time Mihari invited guests over unannounced. The three are confused with Miyo saying that she thought that they were just having a sleepover. Momiji points out that Mahiro supposedly invited them, and a confused Mahiro notices Mihari's devilish smile. Mahiro wonders what Mihari is planning with a sleepover.

Miyo asks Mahiro if she was playing a game, and Asahi asks if they can play. Mahiro decides that that sounds great, and that they can all play this fighting game. Mahiro remembers though that only two people can play at a time, so Mihari shows off something she brought for the occasion. She purchased a party game Super Marimo Party that can support four players and remarks that now they can all play together. Mahiro is amazed by the lengths that Mihari is going to. Asahi recongnizes the game, while Momiji asks what it is. Mahiro puts on the game and says that whoever loses gets a punishment, to which Asahi says that she wouldn't have it any other way. As the four start playing, Mihari looks at them and smiles.

After everyone has eaten, it's revealed that the punishment was that whoever lost had to clean up everyone's dishes from dinner. It's revealed by Mihari that Mahiro lost and that she was the one who suggested it in the first place. Mahiro insists that she let them win, while Mihari notes that Mahiro is taking it pretty badly for someone who lost on purpose. She asks Mahiro if it's more fun to play with your friends. Mahiro says that it depends on the game, making Mihari wonder why Mahiro can't be honest with herself.

Mahiro goes to her room where everyone else is waiting and announces that she's back. Momiji thanks her for all of her hard work. Mahiro asks them if they're up for another round, but Momiji says that it is getting late and that they don't want to bother the neighbors. She adds that she worked up a sweat and wants to take a bath, something that Asahi also wants to do. Mahiro agrees, saying that as the host she'll go last and telling them to feel free to go as they please.

Miyo suddenly gets aroused and suggests that they pair up for the baths. Mahiro is confused, and Miyo explains that if they go one at a time, the hot water will get cold. Momiji agrees with the statement. Mahiro realizes that this isn't good, and tells them that they have a water heater in the tub, so they could just reheat it. As she says this, she sees Momiji and Asahi staring at her. Asahi is eager to wash Mahiro's back, while Momiji says that she can do it do, having done so when they bathed together at the hot spring. The two grab Mahiro on either side of her, while Miyo tells them to calm down. She suggest that they reconsider her original ship and go with an Asahi/Momiji pairing. Mahiro notes that Miyo is already thing dirty. She notes that a public bathhouse or hot spring is one thing, but being alone with a naked schoolgirl in a private room could be a problem.

Momiji tells Asahi that she'll rock-paper-scissors her for the right to bathe with Mahiro, and Asahi says that she's on, announcing in advance that she's going to throw "rock". Mahiro tells them to wait a second and tries to come up with a different idea.

As Mihari is taking a bath, Mahiro suddenly barges in, fully naked as well, surprising Mihari. As Mahiro tests the tub, she explains to Mihari that this is her fault and that they're going to bathe together, much to Mihari's shock. As Mahiro settles in the water, crisis having been averted, Mihari turns red with embarrassment wondering what the heck is going on.

It later revealed that Asahi wears a shirt at night with what she thinks is a fish on it, that Mahiro recognizes as a popular video game character.

Characters

 * Mahiro Oyama
 * Mihari Oyama
 * Momiji Hozuki
 * Asahi Ōka
 * Miyo Murosaki

Trivia

 * Mahiro recalls the last time Mihari invited someone over unannounced in "Mahiro's Exciting Weekend".
 * The game that Mihari got for the girls to play Super Marimo Party is a parody of the 2018 Nintendo Switch game Super Mario Party.
 * Momiji recalls the time she bathed with Mahiro at the hot spring in "Mahiro's Panic! At the Hot Spring (Part 1)".
 * The game character on Asahi's pajama top is a parody of the titular character of Pac-Man.