# Gunma murder investigations

> Live situation record from CLSTR: https://clstr.news/situations/gunma-murder-investigations
> Updated: 2026-08-26T12:34:23.000Z. Sources: 3. Developments: 3.

In late July 2026, police in Gunma prefecture re‑arrested 50‑year‑old factory worker Newai Masanao on robbery‑murder charges after he killed a coworker, stole cash, withdrew ¥240,000, and dismembered the victim’s body, which was later found in the Tonegawa River. Investigators are probing a possible dispute between the two men.

In a separate case involving the death of Bokuo Mochizuki, 41‑year‑old Rieko Mochizuki was arrested in Shibukawa for the fatal assault of her husband’s brother. The incident occurred in February 2025, during which the victim was repeatedly kicked in the chest and abdomen. While the suspect initially claimed the man had fallen from a roof, the victim was discovered on the floor of an entranceway. 

On August 26, 2026, the Maebashi District Public Prosecutors Office announced that Rieko Mochizuki would not be prosecuted due to insufficient evidence and the difficulty of proving the facts of the case.

Both incidents illustrate ongoing homicide investigations within Gunma prefecture, involving separate perpetrators and motives but highlighting the region’s law‑enforcement response to violent crimes.

## Timeline

### 2026-08-26: Gunma woman cleared of charges in brother-in-law's death

A 41-year-old woman in Gunma Prefecture will not face prosecution for the death of her brother-in-law after prosecutors determined that the facts of the assault were difficult to prove.

2 sources. https://clstr.news/cluster/gunma-woman-cleared-of-charges-in-brother-in-laws-death

### 2026-08-05: Gunma woman arrested for fatal assault on husband's brother

A 41‑year‑old woman in Shibukawa, Gunma was arrested for killing her husband’s brother after repeatedly kicking him, citing dissatisfaction with his lifestyle.

2 sources. https://clstr.news/cluster/gunma-woman-arrested-for-fatal-assault-on-husbands-brother

### 2026-07-23: Gunma Man Re‑Arrested for Robbery Murder After Dismembered Body Found in Tonegawa

Gunma police will re‑arrest Newai Masanao for robbery murder after he killed, dismembered and dumped his acquaintance’s body in the Tonegawa River, following a cash‑card theft.

2 sources. https://clstr.news/cluster/gunma-man-rearrested-for-robbery-murder-after-dismembered-body-found-in-tonegawa

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Cite as: Gunma murder investigations. CLSTR, https://clstr.news/situations/gunma-murder-investigations