The father arrested on suspicion of murdering his 3-year-old daughter told voluntary questioning before his arrest that he had hit her "as part of discipline" before, sources close to the investigation said, the Mainichi Shimbun reported.
Erena Kanao died after being assaulted at an apartment in Hirakata, Osaka Prefecture. Her body had dozens of bruises, and prefectural police are investigating whether abuse had been repeated routinely.
Kentaro Kanao, 33, is suspected of punching Erena repeatedly in the abdomen and head at the family's apartment on the night of August 2. Police say she died in the early hours of August 3.
On the day of the incident, the father is believed to have had Erena walk up and down a three-step stool as what he called walking practice. Police believe he flew into a rage when she stopped and assaulted her.
Police have not disclosed whether he admits or denies the charge. According to the sources, he told officers before his arrest that he hit her because she would not do as she was told, and that he had hit her as part of discipline before.
Investigators are looking into how the abuse unfolded, citing the bruises and his account as signs it had gone on for some time.
Erena's mother, Riyo Kanao, 33, was also arrested on suspicion of abandoning a person in her care and causing death. Police say she knew of the assault and did not call for help.