<figure id="attachment_453305" aria-describedby="caption-attachment-453305" style="width: 956px" class="wp-caption alignnone"><a href="#" data-ident_hash="8aaa7dcc"><img src="https://res.cloudinary.com/fridaydigital/image/private/t_article_image/wpmedia/2026/01/21b5ad39f7adba451959346b43cfe723.jpg" alt=""></a><figcaption id="caption-attachment-453305" class="wp-caption-text">Yamanaka was sent to prison on January 10, and we wonder what was going through his mind when he killed his friend of 30 years&#8230;</figcaption></figure>
<h3><span class="strongInContent"> He was lying in his room covered in blood.</span></h3>
<p> In this issue of &#8220;After the Incident&#8230;&#8221;, we will follow up on the incident reported by &#8220;FRIDAY Digital&#8221; up to April &#8217;26. This time, we will report on the &#8220;Omori Mansion Murder&#8221; that occurred on January 8, citing a portion of the article we reported on January 13 (figures in parentheses are quotes from the article at that time; the article changed Yamanaka&#8217;s name from &#8220;suspect&#8221; to &#8220;defendant&#8221; at the time).</p>
<hr>
<p> Masahiro Yamanaka (45), a high school classmate and subordinate of the victim, was arrested on January 9 for the murder of Mr. K (44 at the time), who ran an audio equipment company. The crime scene was a room in an apartment in Omori (Ota-ku, Tokyo) where Mr. K lived, and the incident was discovered at around 11:30 a.m. on January 8.</p>
<p><span class="strongInContent"> &#8220;When Mr. K did not show up at the appointed time, an acquaintance who visited the apartment called the police. An officer found Mr. K lying in the room covered in blood, having been stabbed with a knife in at least several places, including his neck and abdomen, and his hands were left with wounds that were probably caused when he resisted.</span></p>
<p><span class="strongInContent"> Since several bloodstains and bloody footprints were found in the hallway and entrance, and the murder weapon was not found in the room, the Metropolitan Police Department&#8217;s Investigation Section 1 ruled it a murder case. A special investigation headquarters was set up at the Omori Police Station to investigate the case,&#8221; said a reporter from the social affairs section of a national newspaper.</span></p>
<div data-friday-ad-slot="AD_inArticle"></div>
<p> At that time, Yamanaka handed the duplicate key to Mr. K&#8217;s room, which had been given to him by a colleague of his at work, to Omori police officers who arrived at the scene after receiving a 110 call. He was interviewed that day, but was cooperative throughout, denying any involvement in the incident.</p>
<p> However, there were ambiguities in some of his statements, and it appears that the police had their eyes on Yamanaka from the beginning. As the police were marking Yamanaka, he left his home early in the morning of the 9th and was about to buy a Shinkansen ticket at Tokyo Station when he was asked to voluntarily accompany the police, and was arrested later that day.</p>
<p> Yamanaka <span class="strongInContent">said, &#8220;I was dissatisfied with Mr. K&#8217;s attitude toward me, so I went to his home to express my opinion. I sprayed him with insecticide, which was at his front door, and when he flinched, I stabbed him in the neck. He</span> admitted to stabbing Mr. K, but denied some of the charges, saying that <span class="strongInContent">he did not intend to kill him.</span></p>
<div data-friday-ad-slot="AD_inArticle"></div>
<p> Mr. K. and Yamanaka were boss and subordinate at the company, but they had been high school classmates and friends for 30 years. They called each other <span class="strongInContent">&#8220;XX-chan&#8221; and &#8220;Maa</span>,&#8221; and often went out drinking and on trips together. However, their relationship gradually changed after Mr. K invited Ms. Yamanaka to work at his company and they started working together. The article at that time introduces the following testimony.</p>
<p><span class="strongInContent"> &#8220;It seems that the two of them rarely showed up together at the restaurants where they used to go out for drinks together until then. Yamanaka&#8217;s mother also told the interviewer, &#8220;He seemed to be dissatisfied with his work,&#8221; and he himself stated, &#8220;I was dissatisfied with his lack of appreciation for his employees and his poor language. She said that because she could not convey her dissatisfaction, she &#8216;came to think that if she could not understand by talking, I needed to make her change her mind even if I had to hurt her.</span></p>
<p><span class="strongInContent"> He also stated that his bonus, which had been 1.5 months, was reduced to 1 month, and that he was not told why.</span></p>
<p> At the time, Yamanaka denied any intent to kill, saying that he <span class="strongInContent">did not intend to kill and that he took the knife to threaten the victim</span>, but it has since become clear that the crime was premeditated.</p>
<div data-friday-nextpage-lead=" It was a premeditated crime!"></div>
<h3><span class="strongInContent">The charge was changed to &#8220;robbery-homicide.&#8221;</span></h3>
<p><span class="strongInContent"> The security camera at the crime scene showed Yamanaka two days before the incident, suggesting that he may have been casing the place. Also, on the day of the crime, Yamanaka changed his clothes before and after the incident; there were bloody footprints in the bathroom and dressing room of Ms. K&#8217;s room, suggesting that he may have washed himself after the crime.</span></p>
<p><span class="strongInContent"> Furthermore, it is believed that when he left the room, he locked the room with the key that Mr. K had with him, possibly to delay the discovery of the body. The key appears to have been deposited in the mailbox on the door and was found inside the front door.</span></p>
<p><span class="strongInContent"> He then took a cab and dumped the plastic bag containing the clothes he was wearing at the time of the crime, a knife, and other items at a garbage dump in an apartment building in Ota Ward, where he used to live.</span></p>
<div data-friday-ad-slot="AD_inArticle"></div>
<p> Yamanaka was indicted for murder on January 29. However, the case took an unexpected turn on April 8, when prosecutors requested the Tokyo District Court to change the charge to robbery-homicide. According to the indictment after the change of charge, Yamanaka stabbed Mr. K, who owed him 440,000 yen, in the neck with a knife and killed him, thereby evading repayment of the debt and robbing him of approximately 160,000 yen in cash.</p>
<div data-friday-ad-slot="AD_inArticle"></div>
<p><span class="strongInContent"> During the interrogation, it was revealed that Yamanaka had borrowed money from acquaintances, including Mr. K. The police also found that Mr. K.&#8217;s wallet, which was left at the scene of the crime, had been stolen. There were also signs that cash had been removed from Mr. K&#8217;s wallet, which was left at the scene.</span></p>
<p> Was money, rather than a business grudge, the reason for taking possession of a friend of 30 years?</p>
<p> As of May 1, no date has been set for the trial.</p>

<div data-friday-nextpage-lead=" Photo: Yamanaka showed a &quot;scary face&quot; for a moment."></div>
<figure id="attachment_453303" aria-describedby="caption-attachment-453303" style="width: 2986px" class="wp-caption alignnone"><a href="#" data-ident_hash="f9b133cb"><img src="https://res.cloudinary.com/fridaydigital/image/private/t_article_image/wpmedia/2026/01/ea2b193bf9e346f400b9374d5257e051.jpg" alt=""></a><figcaption id="caption-attachment-453303" class="wp-caption-text">He was mostly face down in the car.</figcaption></figure>
<div data-friday-ad-slot="AD_inArticle"></div>
<figure id="attachment_453304" aria-describedby="caption-attachment-453304" style="width: 2986px" class="wp-caption alignnone"><a href="#" data-ident_hash="54d1b8fa"><img src="https://res.cloudinary.com/fridaydigital/image/private/t_article_image/wpmedia/2026/01/6dc50977902c06e4325ee4fddea35b2b.jpg" alt=""></a><figcaption id="caption-attachment-453304" class="wp-caption-text"> At the time of his arrest, he had stated that he had been dissatisfied with Mr. K and had visited his home to express his opinions. &#8230;&#8230;</figcaption></figure>
<div data-friday-ad-slot="AD_inArticle"></div>
<figure id="attachment_453302" aria-describedby="caption-attachment-453302" style="width: 1211px" class="wp-caption alignnone"><a href="#" data-ident_hash="c206021c"><img src="https://res.cloudinary.com/fridaydigital/image/private/t_article_image/wpmedia/2026/01/9ab4cdf4336489c662bdc4219ebca950.jpg" alt=""></a><figcaption id="caption-attachment-453302" class="wp-caption-text"> He looked up for a moment and then glared at us with sharp eyes.</figcaption></figure>


 Shinji Hasuo

 This month's "After the Incident..." follows the "After the Incident" that took place between January and April of this year, focusing on the "Murder of a Boss at the Omori Mansion" that occurred in January. The case is about the "Omori Mansion Boss Murder" that took place in January. At first, it was thought to be a murder out of resentment, but then the tide changed. ......

 After the Incident...] January to April '26 (1)

Murder of the boss at the Omori Mansion: The &#8220;flow&#8221; of the case changed from &#8220;murder&#8221; to &#8220;robbery-homicide&#8221; three months after his arrest.

Murder of the boss at the Omori Mansion: The “flow” of the case changed from “murder” to “robbery-homicide” three months after his arrest.

Access Ranking