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Kenji
Inspector, we have a case.
A limited edition chronograph disappeared during a private viewing after closing hours.
The store was dark for 20 seconds.
However, there was a blind spot for 80 seconds until the surveillance cameras were restored.
Neither the front entrance nor the emergency exit alarms were triggered.
This means the culprit is still inside the store.
A limited edition chronograph disappeared during a private viewing after closing hours.
The store was dark for 20 seconds.
However, there was a blind spot for 80 seconds until the surveillance cameras were restored.
Neither the front entrance nor the emergency exit alarms were triggered.
This means the culprit is still inside the store.
Inspector
Then, before we check their bags, let's see the watches of the three suspects.
Kenji
You want to see their watches before their bags?
Are you considering the possibility that the culprit swallowed the watch?
Are you considering the possibility that the culprit swallowed the watch?
Inspector
People make excuses.
But watches preserve time exactly as it was moved.
Someone who misinterprets it can sometimes destroy their own alibi with their own watch.
But watches preserve time exactly as it was moved.
Someone who misinterprets it can sometimes destroy their own alibi with their own watch.
CASE FILE 28: The Case of the Missing Limited Edition Chronograph
- Incident Time: 19:47:05. Store lights and surveillance cameras stopped.
- Lights Restored: 19:47:25. Darkness lasted 20 seconds.
- Cameras Restored: 19:48:25. Blind spot in surveillance lasted 80 seconds.
- Stolen Item: Hand-wound chronograph, 50 pieces limited worldwide.
- Exits: No record of front entrance or emergency exit being opened or closed.
- Display Stand: No damage. Watch disappeared from the viewing tray.
- Suspects in Store: 3 people.
① Three Suspects. All Had Reason to Touch the Watch.
Suspect A: Shu Manabe
52 years old, watch collector
Prospective buyer. Was negotiating the price until just before the incident and had the limited edition chronograph on his wrist.
Suspect B: Rena Shiraishi
29 years old, product photographer
Carrying a large camera bag. Was taking close-up shots of the watch until just before the incident.
Suspect C: Shingo Kuroda
38 years old, floor manager
Claimed he ran to the breaker room immediately after the power outage. Knowledgeable about store equipment.
Kenji
The culprit is Mr. Manabe.
He couldn't buy the watch he wanted.
There's a power outage.
The watch disappears.
My deduction is faster than instant noodles.
He couldn't buy the watch he wanted.
There's a power outage.
The watch disappears.
My deduction is faster than instant noodles.
Inspector
A deduction made too quickly is usually missing the hot water.
"Wanting it" might be a motive, but it doesn't establish an alibi for the time of the crime.
First, let's compare the time testimonies of the three.
"Wanting it" might be a motive, but it doesn't establish an alibi for the time of the crime.
First, let's compare the time testimonies of the three.
② The "Voice of a Watch" Heard in the Dark
Manabe's Testimony: "From the moment the power went out, I didn't move from the sofa. I activated my watch's minute repeater to know the time. You all must have heard it too."
Kenji
I certainly did.
Seven low tones.
Three tones of two different pitches.
Two high tones.
I remember it because the watch suddenly started a xylophone recital in the dark.
Seven low tones.
Three tones of two different pitches.
Two high tones.
I remember it because the watch suddenly started a xylophone recital in the dark.
Inspector
Seven o'clock, 45 minutes, and 2 minutes.
The minute repeater chimed 7:47.
And the sound came from the back left sofa where Mr. Manabe was sitting.
At least immediately after the power outage, he was there.
The minute repeater chimed 7:47.
And the sound came from the back left sofa where Mr. Manabe was sitting.
At least immediately after the power outage, he was there.
Kenji
The wristwatch is on the witness stand.
And its testimony is more specific than mine.
I would just say, "It was roughly nighttime."
And its testimony is more specific than mine.
I would just say, "It was roughly nighttime."
Clue 1: Minute Repeater
A minute repeater is a complex mechanism that, when activated, tells the current time audibly. Typically, it chimes low for "hours," a combination of high and low tones for "quarter hours," and high tones for "remaining minutes."
The seven, three, and two chimes indicated 7 hours + 45 minutes + 2 minutes, which is 19:47. The location of the sound and the time support Manabe's testimony.
③ The "Watch 7 Minutes Ahead" in the Photo
Shiraishi's Testimony: "During the power outage, I was checking my camera settings. I accidentally took a picture. The shooting time is 19:47:12."
Discrepancy in the Evidence Photo
The photo data recorded 19:47:12. However, Ms. Shiraishi's watch, reflected in the polished showcase, showed 19:54.
Kenji
A watch from seven minutes in the future is in a photo from seven minutes ago.
Ms. Shiraishi, you traveled back in time.
Do you have a small time machine in your camera bag?
Ms. Shiraishi, you traveled back in time.
Do you have a small time machine in your camera bag?
Inspector
Before suspecting a time machine, let's compare the watch to a reference clock.
Inspector
Ms. Shiraishi's watch is still seven minutes fast compared to the accurate time.
She deliberately set it ahead to prevent being late.
Therefore, the 19:54 in the photo is actually 19:47.
It doesn't contradict the photo data.
She deliberately set it ahead to prevent being late.
Therefore, the 19:54 in the photo is actually 19:47.
It doesn't contradict the photo data.
Kenji
I also used to set my clock fast to avoid being late.
After three days, my brain learned "this is seven minutes fast," and I ended up sleeping an extra seven minutes.
After three days, my brain learned "this is seven minutes fast," and I ended up sleeping an extra seven minutes.
The reflection in the photo also showed Mr. Manabe on the sofa.
The minute repeater's sound and the photo match, reinforcing Manabe's alibi.
The minute repeater's sound and the photo match, reinforcing Manabe's alibi.
④ The Last Suspect's "180 km/h Alibi"
Kuroda's Testimony: "As soon as the power went out, I ran 50 meters to the breaker room, restored the lights, and returned. That's 100 meters round trip in 20 seconds. I measured it with my chronograph. The central hand shows 20 seconds, and the tachymeter shows 180."
Kenji
180 km/h!
He's not just a culprit; the acting store manager is a bullet train.
You should prepare tracks for him, not a commuter pass.
He's not just a culprit; the acting store manager is a bullet train.
You should prepare tracks for him, not a commuter pass.
Inspector
The 180 on the tachymeter doesn't mean Mr. Kuroda actually ran at 180 km/h.
A typical tachymeter is a scale that converts the seconds taken to travel a known unit of distance into speed per hour.
A typical tachymeter is a scale that converts the seconds taken to travel a known unit of distance into speed per hour.
Kenji
So, the numbers on the bezel are a conversion table, not a speedometer.
It's like trying to measure your body temperature by looking at a road sign.
It's like trying to measure your body temperature by looking at a road sign.
⑤ For 100 Meters, It's 18 km/h, Not 180.
Tachymeter reading × actual distance (km)
Kuroda's round trip distance is 100m = 0.1km
180 × 0.1 = 18km/h
Inspector
If it's 100 meters in 20 seconds, the average speed is 18 km/h.
That's a very hurried run, but within human capabilities.
The tachymeter numbers can only be used directly when measuring a standard unit like 1 km or 1 mile.
That's a very hurried run, but within human capabilities.
The tachymeter numbers can only be used directly when measuring a standard unit like 1 km or 1 mile.
Kenji
He's been demoted from a bullet train to a hurried office worker.
But if it was a 20-second round trip, he probably didn't have time to steal the watch.
But if it was a 20-second round trip, he probably didn't have time to steal the watch.
Inspector
If it really was 20 seconds.
Clue 2: A Tachymeter Does Not Automatically Measure Distance
- 20-second position is 180: If 1km is covered in 20 seconds, it's 180 km/h.
- If 500m, it's 90km/h: 180 × 0.5.
- If 100m, it's 18km/h: 180 × 0.1.
- Display is average speed: Not instantaneous maximum speed.
- If the distance premise is removed, the numbers lose their meaning.
⑥ In the Shadow of the Large Central Hand, a "Small 1 Minute" Was Moving
Inspector
Mr. Kuroda. Please let me see that watch a little closer.
Inspector
The central chronograph second hand certainly shows 20 seconds.
However, the minute totalizer at the 3 o'clock position is not at zero.
The hand is pointing to "1".
However, the minute totalizer at the 3 o'clock position is not at zero.
The hand is pointing to "1".
Kenji
One minute, and twenty seconds...
A total of 80 seconds?
A total of 80 seconds?
Inspector
Precisely.
Mr. Kuroda's chronograph recorded not 20 seconds.
It recorded 1 minute and 20 seconds.
A typical one-revolution tachymeter is read directly under the assumption that one unit is passed within 60 seconds.
After a full revolution, you cannot read "180" by only looking at the central hand.
Mr. Kuroda's chronograph recorded not 20 seconds.
It recorded 1 minute and 20 seconds.
A typical one-revolution tachymeter is read directly under the assumption that one unit is passed within 60 seconds.
After a full revolution, you cannot read "180" by only looking at the central hand.
Kenji
The culprit wasn't caught by the most prominent central hand, but by a small circle in the corner?
At my company, too, the person who's been silent in a meeting sometimes turns everything around at the end.
At my company, too, the person who's been silent in a meeting sometimes turns everything around at the end.
Decisive Clue for the Reader:
Kuroda's watch showed the central hand at the 20-second position and the minute totalizer at the 1-minute position. The elapsed time displayed was "1 minute 20 seconds = 80 seconds."
Kuroda's watch showed the central hand at the 20-second position and the minute totalizer at the 1-minute position. The elapsed time displayed was "1 minute 20 seconds = 80 seconds."
⑦ 80 Seconds Perfectly Coincided with the Surveillance Camera Blind Spot
Two "80 Seconds"
| Lights Out | Darkness: 20 seconds |
|---|---|
| Surveillance Record | Camera Blind Spot: 80 seconds |
| Kuroda's Chronograph | Minute totalizer 1 minute + central second hand 20 seconds: 80 seconds |
| Kuroda's Explanation | "Round trip to the breaker room was 20 seconds" |
Inspector
Mr. Kuroda wasn't measuring the time he ran.
He was measuring the length of the blind spot from when the lights went out until the surveillance cameras were restored.
The 20 seconds on the central hand coincidentally matched the duration of darkness. But if you read the minute totalizer, the watch recorded the 80 seconds of camera downtime.
He was measuring the length of the blind spot from when the lights went out until the surveillance cameras were restored.
The 20 seconds on the central hand coincidentally matched the duration of darkness. But if you read the minute totalizer, the watch recorded the 80 seconds of camera downtime.
Kenji
But Mr. Kuroda was supposed to be in the breaker room, right?
Inspector
The seal on the breaker room door was unbroken.
The door was never opened.
The lights were set to automatically restore after 20 seconds by a control timer for the private viewing.
Meanwhile, the surveillance camera recorder takes 80 seconds to restart.
Only the floor manager knew these two timings and could have changed the lighting settings.
The door was never opened.
The lights were set to automatically restore after 20 seconds by a control timer for the private viewing.
Meanwhile, the surveillance camera recorder takes 80 seconds to restart.
Only the floor manager knew these two timings and could have changed the lighting settings.
Kenji
He pretended to run, but in reality, he stayed in the dark.
And he only showed the 20 seconds on the central hand,
hiding the remaining minute in the small sub-dial compartment.
And he only showed the 20 seconds on the central hand,
hiding the remaining minute in the small sub-dial compartment.
⑧ Crime Reenactment. Kuroda Created an Alibi "Without Running."
Crime Procedure During 80 Seconds
- Kuroda pre-set the lighting control for the private viewing to stop for 20 seconds.
- Immediately after the power outage, he started his chronograph.
- Shouting "I'm going to the breaker room," he took the watch from the display stand during the initial 20 seconds of darkness.
- Even after the lights were restored, the cameras were still off, so he hid the watch in a leather tool roll in a blind spot in the service aisle.
- After 80 seconds, he confirmed the surveillance camera's recovery light and stopped his chronograph.
- He showed only the 20 seconds on the central hand and falsely testified, "The round trip was 20 seconds."
Inspector
Mr. Kuroda. You thought everyone would believe the big numbers on the tachymeter.
However, a chronograph counts not only seconds but also minutes.
The watch didn't erase the minute you tried to hide.
However, a chronograph counts not only seconds but also minutes.
The watch didn't erase the minute you tried to hide.
Kenji
Shining a spotlight on the central hand and treating the minute totalizer as an extra was his downfall.
Even small roles read the entire script.
Even small roles read the entire script.
⑨ The Culprit is Floor Manager, Shingo Kuroda
The culprit is you.
Inspector: "Shingo Kuroda. You stole the limited edition chronograph."
Kenji
Please check Mr. Kuroda's tool roll.
However, if I open it, there's a chance I'll scatter all the spring bars on the floor,
so I'll leave it to you, Inspector.
However, if I open it, there's a chance I'll scatter all the spring bars on the floor,
so I'll leave it to you, Inspector.
Inspector
The leather lining is unnaturally double-layered.
Recovered Stolen Item
The missing limited edition chronograph was found in a hidden pocket of the tool roll. The watch was wrapped in protective cloth, ready to be taken out.
Kuroda's Confession: "I needed money to cover trading losses. I intended to take it during the power outage and retrieve it after closing. I thought no one would look at the small totalizer if the central hand showed 20 seconds."
Inspector
Big numbers attract attention.
But the truth doesn't always speak loudly.
This time, a minute totalizer just a few millimeters in diameter testified to all 80 seconds.
But the truth doesn't always speak loudly.
This time, a minute totalizer just a few millimeters in diameter testified to all 80 seconds.
⑩ After the Incident, Kenji Records "300 km/h" Again
Kenji
Inspector, look.
10 meters from the entrance to the counter in 12 seconds.
The tachymeter reads 300.
I'm finally a customer service staff member at 300 km/h.
10 meters from the entrance to the counter in 12 seconds.
The tachymeter reads 300.
I'm finally a customer service staff member at 300 km/h.
Inspector
10 meters is 0.01 km.
300 × 0.01 = 3 km/h.
You're just walking normally.
300 × 0.01 = 3 km/h.
You're just walking normally.
Kenji
The case is solved, but my speed has suddenly been brought back to reality.
Inspector
(Perhaps the next thing I need to apprehend is Kenji's unit conversion...)
Conclusion: A Watch Records Even a Culprit's "Omitted Minute"
Inspector
The culprit in this case used the large "180" on the tachymeter to draw everyone's attention to the central hand.
However, reading a tachymeter requires a distance premise.
For 100 meters, the reading is one-tenth of the displayed value.
Furthermore, with a chronograph, one must check not only the central hand but also all totalizers, including the minute totalizer.
Central hand at 20 seconds, minute totalizer at 1 minute.
The total is 80 seconds.
That matched the time the surveillance cameras were off.
The watch did not lie. The person who lied only showed a part of the watch.
However, reading a tachymeter requires a distance premise.
For 100 meters, the reading is one-tenth of the displayed value.
Furthermore, with a chronograph, one must check not only the central hand but also all totalizers, including the minute totalizer.
Central hand at 20 seconds, minute totalizer at 1 minute.
The total is 80 seconds.
That matched the time the surveillance cameras were off.
The watch did not lie. The person who lied only showed a part of the watch.
What the Case Teaches Us About Tachymeters and Chronographs
- A tachymeter requires a known distance: The numbers alone do not represent actual speed.
- For 100m, it's 0.1 times the display: Adjust according to distance.
- It shows average speed for the interval: Not instantaneous maximum speed.
- Don't just look at the central second hand: Read the elapsed time by also checking the minute and hour totalizers.
- A typical one-revolution type should not be read directly beyond 60 seconds: The central hand returns to the same position.
※Tachymeter scale range, totalizer arrangement, measurement limits, and operating methods vary by model. The incident, characters, and limited edition watch in this story are fictional. When operating an actual watch, prioritize the instruction manual for that model and the guidance from the retailer/manufacturer.
Key Deduction Points for This Case
- Don't assume the culprit based solely on motive; compare the time testimonies of each individual.
- Watch displays may not be exact, so cross-reference with a reference clock.
- When using a chronograph, look at all totalizers, not just the central hand.
- Read a tachymeter by aligning "distance, elapsed time, and units."
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