Multiple choice system: Conan World

Everyone in the room turned toward the direction of the sound.

They saw Kojima Genta, who had found a hood belonging to the Masked Superman costume, and had even put it on his own head.

Wearing the Masked Superman hood, Kojima Genta excitedly shouted, transformed as if he had become the superhero himself.

"Hey, Genta, take that off immediately! That could be important evidence!"

Dr. Agasa was startled and quickly stepped forward, urging Genta to remove the hood.

However, just as Dr. Agasa reached Genta, the boy, still wearing the Masked Superman hood, wobbled as if he were drunk, staggered twice, and collapsed to the ground.

"Genta!"

Conan and Haibara Ai screamed, rushing to Genta's side.

Haibara Ai removed the Masked Superman hood from Genta's head and immediately noticed his trance-like state. He appeared utterly weak.

She reached out to check Genta's eyes and saw that they were red and teary.

"There's hydrogen sulfide inside this hood!"

Haibara Ai instantly recognized that Genta was suffering from hydrogen sulfide poisoning.

The detectives nearby were alarmed by Haibara's shout.

A police officer quickly brought over a detector and measured the hydrogen sulfide concentration inside the Masked Superman hood.

The test result read 90 ppm, or 0.009%.

At that concentration, hydrogen sulfide can cause symptoms like dizziness and nausea.

For a child like Genta, the exposure was enough to make him lose consciousness in a short period of time.

"Fortunately, the hydrogen sulfide concentration isn't too high. Genta probably inhaled too much within a short span of time and fainted," Haibara Ai sighed in relief and spoke softly.

Conan stared at the Masked Superman hood, and at last, one of the mysteries of the case became clear to him.

"Originally, we thought the culprit must have produced hydrogen sulfide gas inside Takeshi Furusawa's room.

But since gas evaporates, it was strange that there wasn't any trace of hydrogen sulfide in the air at the crime scene.

However, if the culprit only intended to kill one person, there wouldn't be any need to produce a large quantity of hydrogen sulfide gas.

The killer just needed to produce the gas in a sealed container like this hood, place the hood on Takeshi Furusawa's head, and then block the ventilation holes to carry out the murder with a small amount of gas.

In this way, even if a bit of hydrogen sulfide escaped, it wouldn't significantly affect the air in the room."

Conan had uncovered the killer's method of committing the murder.

"All that remains is to figure out how the culprit produced the hydrogen sulfide gas."

Although Genta had only fainted briefly, the detectives called for an ambulance just to be safe.

At the same time, forensic officers collected the Masked Superman hood, used by the killer to create the hydrogen sulfide gas, as evidence.

"Can you determine how the hydrogen sulfide was produced?" Conan asked Haibara Ai quietly.

"It's possible to identify the ingredients left behind before the reaction, but pinpointing exactly what they were could take some time," Haibara Ai replied.

After briefly discussing the matter with Haibara, Conan went to search the rooms of Mayumi Motoki and Shoichi Matsutani.

That's when something caught his attention.

Shoichi Matsutani's suitcase wasn't very large and was packed tightly with belongings, clearly unable to fit the black suitcase used to transport the body.

Mayumi Motoki, on the other hand, had a much larger suitcase—large enough to fit a smaller suitcase inside it.

Initially, both Conan and most of the detectives present believed that Mayumi Motoki, the first person to discover the body, wasn't highly suspicious.

As a woman who didn't appear to have much physical strength, it seemed unlikely that she could commit murder and dispose of the body all by herself.

However, after Akikawa Kyousuke mentioned overhearing Mayumi Motoki and Shoichi Matsutani privately discussing Furusawa Takeshi's murder,

The detectives began to suspect that Mayumi Motoki and Shoichi Matsutani might have worked together to carry out the murder.

In that case, the suspicion on Mayumi Motoki became much greater.

However, after searching their rooms and belongings, the police found no suspicious chemicals.

"Could it be that the killer disposed of the materials used to produce the hydrogen sulfide when they discarded the suitcase?

Or maybe they only brought just enough to produce the gas and used all of it in the reaction?"

A detective from the Kanagawa Prefectural Police Department asked Dr. Agasa.

"Even if they used it all, there must still be containers for holding the hydrogen sulfide-generating substances and for the acid used in the reaction.

Also, I doubt they could control the dosage with such precision," Haibara Ai replied.

Following Haibara Ai's reasoning, Conan went with her to re-examine the rooms of Mayumi Motoki and Shoichi Matsutani.

That's when Conan noticed that the bathtub in Shoichi Matsutani's room had been used.

In Matsutani's belongings, Conan also found a used bath additive.

It's not unusual for Japanese people to use bath products during a soak.

But the problem lay in the type of bath additive Shoichi Matsutani used—it was a branded product from Kosenan, the hotel's own line.

This bath additive claimed to perfectly replicate the experience of soaking in Kosenan's natural hot springs.

This immediately raised Conan's suspicions.

'Why would Shoichi Matsutani, who had checked into a hot spring hotel, still need to use bath additives in his room?

Even if he wanted a soak, why would he use the same bath additive when he could enjoy the real hot springs downstairs?

No matter how you think about it, the real hot springs are much better than a chemically-created imitation, aren't they?

Unless his purpose wasn't to bathe at all, but to use the bath additive for something else.'

Conan's thoughts raced as he quickly checked the ingredients list of the Kosenan bath additive.

As expected, Conan soon discovered magnesium sulfide listed among the ingredients.

Magnesium sulfide is often included in bath products to provide minerals and create foaming effects, enhancing the experience of natural hot springs.

"Haibara, look at this!"

"Hmm."

Haibara Ai stared intently at the ingredients list of the Kosenan bath additive in Conan's hands and nodded solemnly.

(End of Chapter)