Seven-year-old Yamato Tanooka was met with camera flashes and cheers from dozens of people when he appeared outside the hospital in the city of Hakodate on the northern island of Hokkaido.
"I am fine," Yamato said when a reporter asked how he was feeling.
Police don't intend to press child neglect charges against his parents, police spokesman Shunsuke Kudo said.
Yamato was found in a military training ground hut last Friday, six days after he was reported missing.
The punishment drew public scrutiny, generating debate in Japan over what is considered excessive in disciplining children.
Kudo said police are considering referring the case to a children's welfare center. Miki Kurotatsu with the Hakodate Children's Welfare Center declined to comment on whether the center had received a report from police because it was a private matter.
Wearing a baseball cap and a gray jacket over a T-shirt, Yamato waved at the hospital crowd while holding a greeting card in the shape of an oversized baseball.
Asked what he would like to do, he said he wants to play baseball. He added he would like to go back to school soon and is looking forward to participating in a school sports day.
Before leaving the hospital, his father bowed to the cameras and said, "Thank you." He had told reporters after his son was found that he regretted his action.
