The Bento Box Mystery: The Case of the Missing Mayonnaise
Synopsis
Kazuki Hoshino isn’t your usual main boy. He’s quiet and keeps his bento lunch plain—just rice with salted plum. Even so, school life isn’t easy for him. He wants to grow braver this year—dare to speak, maybe join after-school club.
The real trouble starts on Monday. In the first five minutes of lunch, Kazuki opens his lunch box and finds the mayonnaise packet is missing. The plum is there. The rice is neat. Yet, the most boring thing in his boring lunch—gone.
His desk mate, Ayumu Tanigawa, sees him frown. She teases, “Guess your luck ran dry?” But her tone changes when more people shout—stuff is missing all over the room. Sohara loses her favorite fork, Miki finds her note switched. The whole class begins blaming each other. Some even cry.
Yui Funamoto, head of class council, stands on a chair. She says, “Until we learn who’s doing this, club times are canceled!” Tension spikes. Club dreams break. Who would even want to do this? Would you have kept calm in such room?
The club Kazuki wants, Mystery Research, jumps in.
Satoru Murakami says, “We’re on the job. But we need a field lead.” All eyes run to Kazuki. His blush grows. He wants to fix this too, but leads? With his heart so weak?
Reluctant but pushed on by Ayumu, Kazuki asks, “If I help, does the mystery club take me for good?” Satoru grins, “Solve it and you have a place with us, promise!”
A team of five gathers. Ayumu has sharp memory. Natsumi can draw room detail. Ryo watches the hall from outside.

Kazuki’s group finds clues: no footprints, no grease smudge, only a strand of tape by the window that wasn’t there before. Could the thief slip in through that small space? Or is there a trick?
Back at home, Kazuki can’t let go. “Why mine? Why now? Who’s planning ahead?” His sister jokes that rice isn’t worth stealing, but she helps him recreate the scene using stuffed toys and shoe boxes. Is this how real detectives work, for small puzzles? Or is the truth much bigger?
The next day, lunch comes with dread. This time, three students forget to bring food and two push shoves past Kazuki by accident. In that crowd, Ayumu reminds him of one fast boy: Jin. He’s last one by tables, but leaves quick whenever someone shouts. Suspicion rises.
During club period that’s still banned, the group meets in secret behind the PE stall. Natsumi sketches Jin’s route between halls. Ryo found wrappers under the old science desk probably dropped a day before.
“There might be more than one!” Kazuki tells the group.
Add in Miki, who whispers out someone’s heard feet rustling overhead right after lunch began the first day things vanished. The team checks the beams, using flashlights. Satoru stands below with a broom in case anyone falls. Turns out, there’s an access panel that’s loose. Enough for something—or someone—to reach into lockers and unlock ones that aren’t fully shut.
Ayumu grins. “Got ’em! Let’s play bait.”
Friday, Kazuki puts a fake sandwich in his usual spot, this time topped with a hot chili sauce instead of mayo. They wire a rubber snake and a popper to it. The rest waits in hiding. Wouldn’t you want to see how this spot goes?

When the culprit reaches, two hands grab it at once—it’s Jin and also Miki’s little brother, Takuto! Caught red-handed (and a bit burnt from the chili). Laughter fills the hall. Satoru claps Kazuki’s back: “You led this, you belong.”
Yui restores club hour. Miki forgives Takuto after he says he just wanted to leave notes for his birthday wish, but Jin confesses he took food as a dare. All get one day’s cleaning and lunch with Kazuki.
Ayumu glances at Kazuki, soft. “You did brave—ready for the real club?”
As Kazuki grins, the last shot closes on a hand switching shoes at the entryway. A silver pin, glowing in sunlight, slips by unnoticed. Could a real culprit hide even deeper in the school shadows?

Are you hungry for more, waiting to uncover who the last thief lurking in the school halls is? Would you trust your club mates now?