Photo/Illutration Nao Hosaka around 2019 (Provided by a family acquaintance)

KOBE--The 34-year-old mother of a boy found beaten to death and dumped in a suitcase in grassland near his home here was charged with his murder July 23, along with her three siblings, investigative sources said.

The suspects are Saki Hosaka, 34, the mother of slain 6-year-old Nao Hosaka, her brother Daichi, 32, and 30-year-old twin sisters Tomomi and Asaka. 

Nao’s body was discovered in June. 

Hyogo prefectural police suspect he was beaten to death with a metal pipe on June 19.

Nao’s body bore numerous bruises, mainly on his back, and the cause of death was likely traumatic shock, sources close to the investigation said.

Due to the severity of the beating, police are weighing additional charges that include abandonment of a body and failing to take the boy to a hospital for treatment of his injuries.

Police concluded that the suspects had either an intent to kill or an “unintentional intent” to let the boy die, thereby meriting the charge of murder, the sources said.

The family consisted of six members, including Nao and his 57-year-old grandmother. They lived together at an apartment in the city’s Nishi Ward.

Police said some of the accused are claiming other family members and not themselves were responsible for beating Nao to death. Police seized several stick-shaped objects, including a metal pipe, from their home.

The four were initially arrested June 22 on suspicion of injuring and confining Nao’s grandmother between March and June in the closet of their apartment.

They were rearrested July 13 on suspicion of abandoning Nao’s body in a suitcase and dumping it in a grassy area near his home.

(This article was written by Akari Sugiyama, Saori Kuroda and Tomoya Takaki.)