The three suspects, Kyousuke Akikawa, Mayumi Motoki, and Shoichi Matsutani, remained on the first floor of Kosen-an under the watchful eyes of the criminal police.
Motoki Mayumi and Matsutani Shoichi were visibly hostile toward Akikawa Kyousuke because of his "accusations."
However, Akikawa Kyousuke didn't seem to care.
He sat on a chair, ignoring the glares from Mayumi Motoki and Shoichi Matsutani, quietly observing the actions of the criminal police on the scene.
---
About ten minutes later, a police officer returned with a black suitcase.
Then, the forensic team began to check the suitcase for fingerprints.
"The suitcase used to dispose of the body has been found," Akikawa Kyousuke thought to himself as he glanced at Shoichi Matsutani and Mayumi Motoki.
He noticed that neither of them showed the slightest panic at the discovery of the suitcase.
---
Over twenty minutes later, another police officer came downstairs.
He headed straight for the souvenir shop on the first floor of the hot spring inn, picked up the bath agents sold there, and began inspecting them.
After a while, the officer approached the staff of Kosen-an with the bath agent in hand and began questioning them.
However, faced with the officer's questioning, the staff members shook their heads with blank expressions.
---
Unlike when the police discovered the suitcase, this time, upon seeing the officer with the bath agent questioning the Kosen-an staff, Mayumi Motoki and Shoichi Matsutani's pupils dilated, and their lips tightened slightly.
This did not escape Akikawa Kyousuke's notice.
He recognized these as bodily signs of anxiety and tension.
---
Moreover, Akikawa Kyousuke also observed that the muscles in both suspects' cheeks and jaws were visibly tense.
This led Akikawa Kyousuke to make a new judgment about the case.
---
"They both showed nervousness and anxiety over the bath agent, so it seems they used Kosen-an's bath agent to produce hydrogen sulfide and kill Takeshi Furusawa."
"They were confident in how they handled the suitcase used to dispose of the body and believed it was flawless."
"However, neither of them anticipated that the police would so quickly link the bath agent to the production of hydrogen sulfide."
"If it weren't for the Shinigami elementary student, the police might have been misled."
---
Akikawa Kyousuke had previously claimed to the police that he overheard Mayumi Motoki and Shoichi Matsutani secretly discussing Furusawa Takeshi. In reality, this was a fabrication by Akikawa Kyousuke.
However, neither suspect could prove that Akikawa Kyousuke was lying.
This was because Mayumi Motoki and Shoichi Matsutani did know each other and were indeed accomplices in the murder of Furusawa Takeshi.
---
Akikawa Kyousuke had only briefly interacted with the two during police questioning, but he reached his conclusions based on their behavior.
For instance, when Mayumi Motoki heard the name Takeshi Furusawa, her expression subtly changed. The corners of her mouth twitched downward, and one of her eyebrows raised slightly.
This reaction indicated that Mayumi Motoki harbored a deep resentment for Furusawa Takeshi.
This conflicted with her claim that she did not know Takeshi Furusawa.
---
Additionally, when Mayumi Motoki was considered a suspect because she lacked an alibi for 1:00 a.m., she responded by saying:
"Most people are asleep at that time. How can we possibly have an alibi?"
By using the word "we" to refute the police, Mayumi Motoki inadvertently implicated herself.
If she truly had nothing to do with the case, it would have been more beneficial for her to let the police suspect the other suspects.
There was no reason for her to speak on behalf of the others—unless one of the suspects was someone she knew.
---
Right after Mayumi Motoki made her statement, Shoichi Matsutani immediately followed up, agreeing with her.
This further aroused Akikawa Kyousuke's suspicions about their relationship.
Moreover, Akikawa Kyousuke noticed that Shoichi Matsutani often glanced at Mayumi Motoki while speaking.
However, after making eye contact, Matsutani would quickly avert his gaze.
---
From Matsutani Shoichi's deliberate avoidance of eye contact, Akikawa Kyousuke deduced that he was trying to hide the fact that he and Mayumi Motoki knew each other.
---
This method of deducing someone's thoughts through microexpressions and psychology wasn't foolproof.
But when multiple behaviors consistently pointed to the same conclusion, it was highly likely that the conclusion was correct.
---
Many of Mayumi Motoki and Shoichi Matsutani's actions indicated that they were deliberately concealing their acquaintance.
And Mayumi Motoki, who seemed unrelated to the case, also showed clear disdain for the deceased Takeshi Furusawa.
Thus, Akikawa Kyousuke concluded that this was no coincidence.
It was highly likely that the two had conspired to kill Furusawa Takeshi.
---
Shoichi Matsutani, who appeared to have no motive for the murder, was the perpetrator.
Mayumi Motoki, who seemed incapable of committing the crime, provided Matsutani with the tools to carry it out.
---
Akikawa Kyousuke was neither a police officer nor a detective.
He didn't need to catch the criminals himself, nor did he need to uncover their motive or method.
There was no need for him to provide concrete evidence to prove their guilt.
---
Akikawa Kyousuke simply deduced from their words and actions that they were the culprits.
After revealing this to the Shinigami elementary student, Conan would naturally handle the rest.
---
Having interacted with Conan many times, Akikawa Kyousuke had realized that the young detective had an exceptional ability to find evidence once the murderer was identified.
---
While Akikawa Kyousuke was pondering these thoughts, Conan and the others came downstairs.
The ever-shrewd Dr. Agasa approached Akikawa Kyousuke and the others. Under Conan's guidance, he announced:
---
"The murderer's method has been fully understood."
"The killer used the bath agents sold at Kosen-an to produce hydrogen sulfide gas and then used the hood of Masked Superman to kill Mr. Furusawa."
---
"The murderer is you—
Mr. Matsutani!
And the person who helped Mr. Matsutani commit the murder was you, Miss Motoki."
---
(End of Chapter)