Japanese man, 20, allegedly killed in park by his girlfriend's friends consisting of boys, men & women aged 16-20

A 20-year-old college student was found dead and naked in a park in Hokkaido, Japan, in 2024.

He was discovered to have been beaten to death.

According to The Japan Times, Tomoya Hase was attacked due to problems between him and his girlfriend, Ama Yagihara, who was also 20 at the time.

ETtoday reported that a friend of Yagihara, who knew about the dispute, then gathered several others to "vent their anger" on Hase.

In total, four men between the ages of 16 and 18, Yagihara, and another female, aged 20, were involved in the attack.

Hase was lured to the park by the group, where they brutally assaulted him, stripped him naked, and burned his hair.

Sentences

According to Asahi, on Jun. 25, 2026, Yoto Kawamura, the other woman involved in the assault, was sentenced to 30 years in prison.

She reportedly appealed against her sentence on Jul. 9 and is scheduled to appear as a witness in court on Jul. 14.

Two of the male assailants, both minors at the time of the attack, were sentenced to jail for 20 years and nine to 13 years, respectively.

The proceedings involving the remaining assailants are in process.

A formal verdict is expected for two more of the males on Aug. 7.

On Jul. 13, 2026, one of the assailants, Yuto Kawaguchi, pleaded guilty to all charges brought against him and apologised, adding that the group had done something "truly horrible" to then-college student Hase.

Brutally assaulted

ETtoday reported that Hase had reportedly been hit multiple times in the head and also suffered a fractured lumbar vertebra.

Apart from stripping him naked and burning his hair with a lighter, they also forced him to "apologise".

In addition, they took his credit card to steal money and buy cigarettes, while Hase was left seriously injured and alone in the park.

His body was only discovered by passers-by the next morning.

Prosecution submits video of assault

The group's actions were shown to the court in a video submitted by the prosecution.

They had apparently recorded the assault on their mobile phones,

The main suspect was reportedly seen kicking Hase in the abdomen, causing blood to splatter.

On top of that, Kawaguchi continued to kick the victim in the back when Hase's bones could apparently be heard cracking during the assault.

The Sapporo District Court will conduct the trial in batches, with the final defendant being Asahi Yagihara.