Summary
With a relay in P.E. and a progress test in math Kaori Matsumoto is in a foul mood as she sits in class during break. Even with her friends she doesn't feel any better- the only thing capable of lifting her spirits is observing her crush from afar; the handsome and popular Isaka, a classmate who enjoys basketball. She wishes they could be closer but she isn't good at sports like his childhood friend Sari, who she observes joining the boys.
Suddenly, one of her friends suggest they pass time by drawing on the blackboard. But she finds herself writing down her complaints about math and school. She thinks of it as boring and dislikes it, and for some reason she can't bring herself to enjoy it like everyone else.
As Kaori gets home her older sister questions her poor mood, but Kaori is surprised to see her home so early until she explains that her school is holding it's testing period. Her sisters happiness causes her to further complain -something that's not uncommon of her- and her sister teases her by bringing up the "Execution Blackboard". It's one of the seven mysteries at her school and can be found on the second floor within an abandoned classroom. Whatever one wants to eliminate, they just write it down on the blackboard in red chalk and erase it, then the thing will vanish. She doesn't personally believe it in but several boys claim to have tested it out, and since then the room has been locked up to prevent anyone else from entering.
Kaori has never heard of such a thing, but with nothing better to do she gets up early and heads to school. She isn't surprised to find the door has been locked like her sister claimed, but before she takes off she happens to notice a small slot at the bottom of the door. She checks her surroundings before lifting it and sliding into the room, then she takes out a red piece of chalk and checks again before writing down "Math Progress Tests" and erases it.
Since it's only a lie there shouldn't be any harm in writing it.
However, Kaori is unprepared when during class the Teacher announces that the Progress Tests are going to be discontinued. Everyone is delighted by the news and during her next free period, Kaori -still in shock- returns to the blackboard and wonders if it actually worked. She decides to test it again by writing down Tomato's in School Lunch as she dislikes them, and erases it.
Later, she overhears someone mention that although tomato are on the menu, there's none to be found in the food. Hearing her friends rejoice over this Kaori is elated realizing the mystery of the blackboard is indeed real. What makes it even better is that she's the only person who knows about it because of the Teachers trying to get rid of the rumor and keeping the room locked up. She also discovers that Isaka hates tomato too, which makes her feel happy to know they have something in common.
Kaori feels really good seeing how happy she is beginning to make her classmates, and soon it becomes obvious to her that she can use this blackboard to make everyone even happier!
The second she gets a chance she returns to the abandoned classroom and starts getting to work. She starts by eliminating the relay in P.E. and the stray dog by the west gate that everyone thinks is scary and tries to avoid. She even tries something different by transforming Kurohane -a girl bully who harasses another girl for her homework- and making her someone who is very kind and considerate and does her own homework.
Kaori's happiness grows over time, until one day when she decides to listen to Isaka and his friends chat about how good things have been. Even though nobody knows it's her doing, Kaori is very glad. But suddenly, she hears one of Isaka's friends suggest that it must be Sari who is fixing everything. They assume she spoke to Kurohane and approach her to celebrate her success, but Sari can only quietly observe them with confusion, unsure of how to respond. Kaori is stunned and watches as Isaka and his friends shower Sari with compliments and begin to tease Isaka by claiming he has feelings for her.
An enraged Kaori rushes back to the classroom during her next break. But before she can write anything down she hesitantly steps back, alarmed by what she almost did. She thinks about what led her to this, but them she remembers what else happened later in the hallway. Sari stopped Isaka to ask him if they liked one-another, and his awkward response seemed to confirm that he did.
With her anger restored, Kaori remorselessly writes down Umezawa Sari.
When class resumes Kaori remains silent as everyone begins worrying noticing Sari hasn't shown up. She was there earlier, and they wonder if she might have left early without saying anything, but that isn't like her. In silence Kaori can only think about how much she really, really, really hates Sari- she's such a horrible girl who enjoys the attention she gets from others, and she has no right to think she deserves to stand by Isaka's side. Now that she's out of the way, she can begin to get closer to Isaka.
During their next break Kaori attempts to cheer up Isaka and approaches him. She asks to join them for basketball now that they're missing a member, and Isaka -who appears distraught- agrees, although his friends rudely reject her for being so lousy at sports. He gently chastises their behavior and attempts to enjoy their time together.
Once school ends Isaka prepares to leave for home when he walks by a window and out of the corner of his eye he spots Kaori sneaking into the other school building. Suspicious, he decides to follow after her since she has no reason being in there.
The following day, everyone hears that another classmate, Yamaguchi, has vanished. They are beginning to grow uneasy now that two students have gone missing but Kaori remains indifferent since she's aware of what's actually going on. She then later witnesses another girl begin to bully another girl and take something of hers before leaving. The girl sadly wishes Sari would return to help her, which indirectly angers Kaori again.
Later, a disgusted Kaori makes her way back into the school and to the chalkboard while pondering whose name she should be writing down next. It isn't like she's doing anything wrong, and because there's a bunch of girls sucking up to Isaka now that Sari's gone she has to do something about it. But before she can begin, she is horrified when Isaka calls out to her from the door!
He is incredibly angry over what she's done and be brings up that his own sister told him the rumor. He didn't believe in it but now that he's had proof he has no choice but to do something about it. Kaori is frightened over this and realizing he won't forgive her for what she's done, and in a panic she quickly darts out of the room and attempts to run away. She hides and it dons on her that she can't return to class because he'll tell everybody else, and anybody who holds a grudge on her -like him for ridding of Sari, or the girl who got bullied- could return to this room and try to get rid of her.
She tearfully overhears Isaka locate a Teacher and observes them speaking for a moment before running into the now opened door. They rush up to it and she slams it shut, locking it and approaching the chalkboard as they try opening the door. Isaka yells out to her through the window but she ignores him and takes out the chalk, deciding that before she risks being erased she will get rid of the threats first. But she pauses momentarily, realizing that in her hurry back into the room the Teacher was on the phone will the police. So it will only be a matter of time before everyone finds out!
Suffering a complete meltdown, Kaori quickly writes on the chalkboard everything but me and steps back to observe her work before erasing it. She calms down instantly, but then she notices that she hears nothing. She turns to look around, only to find herself surrounded by white nothingness.
Isaka and the Teacher manage to bust open the door, but to their shock they find that Kaori is missing. The only thing left in her place is the chalk and eraser.
Tropes:
- Be Careful What You Wish For: In order to save herself from the eventual wrath of her classmates and the police, Kaori wishes to erase everything but herself. This effectively means erasing herself from existence, as nothing becomes everything while she's left behind in the resulting White Void Room.
- Hopeless Suitor: Kaori never had a chance with Isaka.
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Moral Event Horizon: Initially Kaori only wanted to do good things with her knowledge of the blackboard and believed she wasn't doing anything wrong. But angered by the credit everyone gave Sari made her try to get rid of her. She stopped herself before she could until remembering earlier, when she eavesdropped on them and found out Isaka returned Sari's feelings. - One of the Guys: Sari, a Tomboy who loves playing basketball with Isaka and his friends.
- Ret-Gone: The blackboard's power is to do this.
- Yandere: Kaori doesn't display this at first, but she reacts very strongly the more she sees Sari and Isaka interact. After getting rid of Sari she also had planned on getting rid of more girls who were trying to get close to Isaka.
