A man charged with abuse that led to the death of his 5-year-old stepdaughter last year told a Tokyo court Friday that he started assaulting her after his efforts at disciplining her did not work.

"My disciplining was unsuccessful, and I started assaulting her as my anger grew," Yudai Funato, 34, said during a questioning session by his defense counsel in a lay judge trial held at the Tokyo District Court over the fatal abuse of Yua.

"I couldn't control my emotions," he said. "I believe it is completely my responsibility."

Funato assaulted Yua at their home in Tokyo's Meguro Ward and deprived her of food from around late January last year, and failed to take her to a hospital when her condition seriously deteriorated the following month for fear it would expose his abuse, according to the indictment.

As a result, she died in March 2018 from sepsis after developing pneumonia, the indictment said. Funato has admitted to most of the charges.

During the first court hearing of his case on Tuesday, prosecutors said Funato's abuse became worse when Yua, her mother Yuri, 27, and a younger brother, moved from Kagawa Prefecture to join him living in Tokyo in January 2018.

He physically abused the girl for failing to live up to his difficult demands, including waking up at 4 a.m., according to the prosecutors.

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Funato told the court he was infuriated to see her asleep after having instructed her to learn how to read a clock at the end of February last year.

He grabbed her by the neck, lifted her up and took her to the bath where he yelled at her to apologize. Funato then sat astride Yua to limit her movements and sprayed cold water on her face with the shower rod.

Funato limited the girl's food intake and rarely allowed her to leave the apartment during her final 39 days of life. She was greatly emaciated and had 170 injuries on her body at the time of death, the prosecutors added.

Funato admitted that she was not given carbohydrates, meat or fish, and there were days when she was only given one meal.

Yua left behind written messages such as "Please forgive me" on a sheet of paper, which prosecutors regarded as pleas for her mistreatment to stop.

The defense counsel said Funato "had high ideals for his family and began to snap at them," and did not abuse them because they were an obstruction.

"My ideal of a family was a bright one with lots of laughter," he said in answering his counsel's questioning.

One of the judges pointed out that Yua was not allowed outside and said, "That sounds far from your ideal."

"It's inconceivable now that I think about it," Funato answered. "I was not in a mental state to be aware of such a thing back then."

The girl's death attracted nationwide attention and prompted Japan to enact revised laws in June this year, banning parents and guardians from physically punishing children and strengthening the ability of child welfare centers to intervene in cases where abuse is suspected.

Yua had twice been taken into protective custody by a child welfare center in Kagawa Prefecture, western Japan. Another center in Tokyo tried to check on her in February last year, but her mother refused to let the officials see her.