Mahiro and the After-School Fright

Mahiro and the After-School Fright (まひろと学校の怪談, Mahiro To Gakkou No Kaidan) is Chapter 54 of Onimai: I'm Now Your Sister!. It was originally published on Pixiv on July 24, 2021.

Summary
Mahiro and Momiji get trapped in the school after-hours by a thunderstorm.

Plot
It's Mahiro and Momiji's turn for bathroom duty, so they stay after school to complete it. Mahiro cleans the toilets while Momiji cleans the floors.

Mahiro remarks that she hates bathroom duty, as even having to change for it is a chore, as they're currently in their gym clothes. Momiji points out that they wouldn't want their uniforms to get dirty. She tells Mahiro to finish fast so they can go, saying that the toilets are scary after school. Mahiro asks Momiji if she's afraid that a ghost might peek over the top to say hello, and does so herself. Momiji gets scared and tells Mahiro to quit it.

When the two are finished, they go to Class 2-B only to find that they stayed after too long and that everyone's gone. Moniji points out that this happened because Mahiro kept playing around. Momiji suggests that they go, saying that it's creepy with no one else around. Mahiro calls Momiji such a scaredy-cat.

Just then thunder and lightning is heard outside, and it starts to rain heavily. Mahiro is shocked at the appearance of an unexpected rainstorm, and Momiji says that she didn't bring her umbrella. Mahiro decides to ask Mihari to come pick them up, but Mihari texts that it'll take about an hour before she's free and apologizes. Momiji says that Kaede is busy with work too, and Mahiro remarks that this is not good.

Mahiro suggests that they'll just have to wait in the library saying that the rain might let up. Momiji hopes that the librarian is still there.

As the two walk down the empty hallway, thunder continues to rumble outside and Mahiro notes that this really does set the vibe. Momiji tells Mahiro to seriously quit it and then gets scared by something. Mahiro asks her what's wrong, and Momiji points down the hallway saying that they'll pass by the science room. Mahiro tries to asks Momiji what the problem is, and Momiji asks what if the anatomy model jumps out at them. Mahiro understands, remembering that that is one of the seven scary stories of the school. Mahiro suggests that they take a detour then, but asks Momiji if she's sure as taking the long way around might be scarier. Momiji just pushes her along telling her that they should do it already.

As they walk, Mahiro thinks to herself that the whole "seven scary stories" thing takes her back, remembering "The Pool Monster", "The Singing Piano", "The Living Statue", and "The Wandering Schoolgirl's Ghost". She tries to remember the last one, and as they get to the stairs she remembers that it "The Thirteenth Step".

Mahiro explains that it is said that stairways that have twelve steps during the day have a thirteenth one at night, but Momiji is in tears and begs Mahiro to stop. Mahiro says that there's no way that it's true and decides to count them to be sure. Mahiro starts counting, but after she counts to four, she and Momiji see the shadowy figure of a girl standing at the top of the stairs. The figure looks at them with a sinister expression and glowing eyes, leading Mahiro and Momiji to realize in horror that it's a ghost.

The two take off running, with Momiji calling Mahiro a jerk and telling her that this is all her fault. Mahiro tells Momiji to wait up, suggesting that it could just be a regular student. Momiji stops after she sees another one at the end of the hall in front of them, with Mahiro wondering what the strange glow coming from it is. Mahiro realizes that they can't just go back, and decides that they'd better hide somewhere. Mahiro calls for a crying Momiji and pulls her into the girl's bathroom where they hide in a stall.

Momiji can't believe that Mahiro took them back to the bathroom, but Mahiro tells her to be quiet as they hear the figure enter the bathroom. The two get increasingly scared as the steps draw closer, and scream out when the figure peers over the top of the stall, wetting themselves in the process.

Mahiro then realizes in disbelief that the figure is Nayuta who thought that the two were playing hide and seek after school. Nayuta explains that she forgot her tablet and came back for it, with Mahiro understanding that that was the glow they saw.

Later, Mahiro and Momiji have changed into their gym clothes with Momiji saying that its a good thing that it wasn't really a ghost. Nayuta is surprised that Momiji is the supersticious type. Momiji tries to deny it, but Mahiro confirms it, all the while thinking what happened was a little scary.

At that moment, Mihari arrives with another umbrella for Mahiro and apologizes that she was so late getting there. Mahiro and Momiji tell Mihari that this is all her fault for taking so long, which Mihari is confused about. She asks them why they're both in their gym clothes. Mahiro and Momiji look at each other for a second and claim that their uniforms got wet from the rain. Mihari understands what really happened and laughs about it.

Meanwhile, the shadowy girl that Mahiro and Momiji saw is shown to have been watching them from a window. She then turns down the hall and vanishes, revealing that she really was a ghost.

Momiji sees the glow from when she vanished, and gets scared. Nayuta tries to tell her that it was just swamp gas.

Characters

 * Mahiro Oyama
 * Mihari Oyama
 * Momiji Hozuki
 * Nayuta Tenkawa
 * Ghost Girl

Trivia

 * First appearance of the Ghost Girl.
 * Mahiro mentions seven scary stories that are associated with the school, all of which reference real life Japanese horror stories as noted by the chapter. There is no consistency between schools, and the specific legends change between them. These are the following ones that are associated with the middle school:
 * "Hanako of the Toilets" features a ghost who haunts school bathrooms and peeks over the top of the stalls to say hello.
 * "The Moving Mannequin" features an anatomy model in the science classroom that jumps out at people to scare them.
 * "The Pool Monster" features a monster in the school pool after hours.
 * "The Singing Piano" features a piano which plays on its own when no one's around.
 * "The Living Statue" feature a statue that comes to life.
 * "The Wandering Schoolgirl's Ghost" features the ghost of a former schoolgirl who wanders the hallways. Revealed to be real in the chapter.
 * "The Thirteenth Step" is a legend saying that the stairways that have twelve steps during the day have a thirteenth step at night.
 * The reason why Mahiro and Momiji changed back into their gym clothes is revealed in the next chapter "Mahiro's Cool Head".