Sushi Chef Kills Coworker with Such Force Knife Snapped—Driven by Long-Held Rage

A tragedy that struck before opening hours

Masato Ishioka (56) hid his face as he was led out of the Ikebukuro Police Station in Tokyo, after noticing the gathered media. His thinning hair was disheveled, stubble covered his mouth, and his expression appeared utterly exhausted.

Ishioka was arrested on July 25 on suspicion of murder. He allegedly stabbed and killed his coworker, Tomoyuki Iwata (32), at a sushi restaurant where they both worked in Nishi-Ikebukuro, Toshima Ward.

“Around 4:30 p.m. on the 25th, a call to emergency services reported that someone’s throat had been slashed at the sushi restaurant,” said a national newspaper crime reporter. “When police arrived, they found Iwata collapsed with blood flowing from multiple wounds to his neck, chest, and abdomen. He was rushed to the hospital but later pronounced dead. At the same time, Ishioka turned himself in at a nearby police box, stating, ‘I stabbed someone.’ He was then arrested for murder.”

A bloodstained kitchen knife from the restaurant was found near where Iwata collapsed. The 30 cm blade had snapped completely at the handle. The attack occurred before business hours, and several other staff members were present in the restaurant at the time.

“Ishioka told investigators that he and the victim didn’t get along and that he had built up anger toward him,” the reporter added. “The broken knife suggests extreme force and rage. Notably, Iwata had no defensive wounds, and other staff said they didn’t hear any argument, indicating that Ishioka may have attacked him without warning.”

Was his resentment one-sided?

On July 1, another colleague murder at work occurred in Ikebukuro. At the Adire Law Office located in the Sunshine 60 Building near the east exit, a 50-year-old male employee stabbed his 36-year-old colleague, Mr. A, multiple times in the throat and neck with a survival knife, killing him. The arrested man reportedly stated, “I felt intimidated by Mr. A’s attitude and gaze and had harbored resentment toward him for some time. He reached his breaking point and stabbed him. I wanted to cause him pain.” The fact that a 50-year-old man killed a 30-year-old colleague also aligns with this incident.

“Around noon, the man crept up behind A, who was working at his desk, and suddenly slashed his throat with a knife without saying a word. He then stabbed him multiple times, targeting his neck. The two worked on the same floor but were in different departments and had separate desks. There was no work-related connection between them, and no staff members had ever seen them talking during break time. The victim, A, was well-liked and relied upon by everyone. The police believe the man had harbored a one-sided grudge against A” (crime reporter).

After the incident, defamatory comments targeting the victim, A, appeared on social media, prompting Adire Law Office to issue the following statement:

“Currently, some online information and social media posts are spreading unfounded speculation suggesting that the victim may have been partially at fault. Based on the information we have at this time, the departments, job responsibilities, and chain of command were separate, and there was no history of the parties being closely involved in work-related matters. We have confirmed that the victim had no fault or blame whatsoever.”

What kind of anger did Ishii, the suspect who allegedly stabbed Iwata suddenly, harbor in his heart, and how did he cultivate that anger into murderous intent? The outcome of the investigation is closely watched.